November 07, 2018

Release Notes for Safari Technology Preview 69

Surfin’ Safari

Safari Technology Preview Release 69 is now available for download for macOS Mojave and macOS High Sierra. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS Mojave and from the Mac App Store’s Updates tab on macOS High Sierra. After updating to macOS Mojave, you may have to reinstall Safari Technology Preview.

This release covers WebKit revisions 237231-237630.


  • Enabled Conic Gradients by default (r237402)


  • Enabled the <datalist> element by default (r237245)
  • Added new image type for the CSS Paint API (r237276)
  • Changed the CSS Painting API to give a 2D rendering context (r237344)
  • Changed the CSS Painting API to parse paint() and store paint callbacks (r237243)
  • Changed Web Animations to not create a DocumentTimeline to suspend or resume animations (r237231)

Intersection Observer

  • Handled zero-area intersections (r237284)

Dark Mode

  • Changed to use a dark appearance scrollbar when the page background is dark or the document supports dark mode (r237466)


  • Implemented BigInt support for ^ (r237296)


  • Added support for MediaKeyEncryptionScheme (r237268)
  • Updated to be able to adapt between H.264 streams with and without EditList (r237271)
  • Updated TextTrack cues to be updated more often than every 250ms (r237376)
  • Fixed timestampOffset to prevent introducing floating-point rounding errors to incoming samples (r237274)
  • Fixed the WebVTT region parameter and value to be separated by : (r237270)

Web Inspector

  • Added corner rounding to the network timing blocks in the Network tab waterfall (r237432)
  • Changed to more aggressively snap timing blocks together in the Network tab (r237430)
  • Fixed CSP JSON request payload without a MIME-type to be pretty-printed (r237396)
  • Added fullscreen enter and exit events in the Timelines and Network waterfalls (r237431)
  • Fixed the Quick Open dialog to show named scripts that appear in the Debugger sidebar (r237327)
  • Fixed the Quick Open dialog for line and column to have a caret indicate the position (r237232)
  • Fixed malformed popovers for function source code (r237401)
  • Prevented the Canvas tab from listening for “space” key press when the tab is not visible (r237560)
  • Improved Canvas Recording loading speed when the “Frame” tree element is expanded (r237436)
  • Updated the Canvas tab to show a warning when the path moves offscreen (r237574)


  • Changed MediaRecorder to fire a stop event when all tracks are ended (r237311)
  • Changed to handle MDNS resolution of candidates through libwebrtc directly (r237568)

Payment Request

  • Implemented MerchantValidationEvent.methodName (r237521)
  • Implemented PaymentResponse.retry() (r237597)
  • Updated PaymentRequest.canMakePayment() to resolve to true whenever Apple Pay is available (r237594)


  • Added a deprecation warning to the console for Web SQL (r237591)
  • Fixed iteration of cursors skipping records if updated or deleted in IndexedDB (r237590)

November 07, 2018 06:00 PM

Michael Catanzaro: Mesa Update Breaks WebKitGTK+ in Fedora 29

Igalia WebKit

If you’re using Fedora and discovered that WebKitGTK+ is displaying blank pages, the cause is a bad mesa update, mesa-18.2.3-1.fc29. This in turn was caused by a GCC bug that resulted in miscompilation of mesa.

To avoid this bug, downgrade to mesa-18.2.2-1.fc29:

$ sudo dnf downgrade mesa*

You can also update to mesa-18.2.4-2.fc29, but this build has not yet reached updates-testing, let alone stable, so downgrading is easier for now. Another workaround is to run your application with accelerated compositing mode disabled, to avoid OpenGL usage:


On the bright side of things, from all the bug reports I’ve received over the past two days I’ve discovered that lots of people use Epiphany and notice when it’s broken. That’s nice!

Huge thanks to Dave Airlie for quickly preparing the fixed mesa update, and to Jakub Jelenik for handling the same for GCC.

By Michael Catanzaro at November 07, 2018 02:28 AM

November 03, 2018

Michael Catanzaro: WebKitGTK+ 2.22.2 and 2.22.3, Media Source Extensions, and YouTube

Igalia WebKit

Last month, I attended the Web Engines Hackfest (hosted by Igalia in A Coruña, Spain) and also the WebKit Contributors Meeting (hosted by Apple in San Jose, California). These are easily the two biggest WebKit development events of the year, and it’s always amazing to meet everyone in person yet again. A Coruña is an amazing city, and every browser developer ought to visit at least once. And the Contributors Meeting is a no-brainer event for WebKit developers.

One of the main discussion points this year was Media Source Extensions (MSE). MSE is basically a way for browsers to control how videos are downloaded. Until recently, if you were to play a YouTube video in Epiphany, you’d notice that the video loads way faster than it does in other browsers. This is because WebKitGTK+ — until recently — had no support for MSE. In other browsers, YouTube uses MSE to limit the speed at which video is downloaded, in order to reduce wasted bandwidth in case you stop watching the video before it ends. But with WebKitGTK+, MSE was not available, so videos would load as quickly as possible. MSE also makes it harder for browsers to offer the ability to download the videos; you’ll notice that neither Firefox nor Chrome offer to download the videos in their context menus, a feature that’s been available in Epiphany for as long as I remember.

So that sounds like it’s good to not have MSE. Well, the downside is that YouTube requires it in order to receive HD videos, to avoid that wasted bandwidth and to make it harder for users to download HD videos. And so WebKitGTK+ users have been limited to 720p video with H.264 and 480p video with WebM, where other browsers had access to 1080p and 1440p video. I’d been stuck with 480p video on Fedora for so long, I’d forgotten that internet video could look good.

Unfortunately, WebKitGTK+ was quite late to implement MSE. All other major browsers turned it on several years ago, but WebKitGTK+ dawdled. There was some code to support MSE, but it didn’t really work, and was disabled. And so it came to pass that, in September of this year, YouTube began to require MSE to access any WebM video, and we had a crisis. We don’t normally enable major new features in stable releases, but this was an exceptional situation and users would not be well-served by delaying until the next release cycle. So within a couple weeks, we were able to release WebKitGTK+ 2.22.2 and Epiphany 3.30.1 (both on September 21), and GStreamer 1.14.4 (on October 2, thanks to Tim-Philipp Müller for expediting that release). Collectively, these releases enabled basic video playback with MSE for users of GNOME 3.30. And if you still use of GNOME 3.28, worry not: you are still supported and can get MSE if you update to Epiphany 3.28.5 and also have the aforementioned versions of WebKitGTK+ and GStreamer.

MSE in WebKitGTK+ 2.22.2 had many rough edges because it was a mad rush to get the feature into a minimally-viable state, but those issues have been polished off in 2.22.3, which we released earlier this week on October 29. Be sure you have WebKitGTK+ 2.22.3, plus GStreamer 1.14.4, for a good experience on YouTube. Unfortunately we can’t provide support for older software versions anymore: if you don’t have GStreamer 1.14.4, then you’ll need to configure WebKitGTK+ with -DENABLE_MEDIA_SOURCE=OFF at build time and suffer from lack of MSE.

Epiphany 3.28.1 uses WebKitSettings to turn on the “enable-mediasource” setting. Turn that on if your application wants MSE now (if it’s a web browser, it certainly does). This setting will be enabled by default in WebKitGTK+ 2.24. Huge thanks to the talented developers who made this feature possible! Enjoy your 1080p and 1440p video.

By Michael Catanzaro at November 03, 2018 04:19 AM

Michael Catanzaro: On WebKit Build Options (Also: How to Accidentally Disable Important Security Features!)

Igalia WebKit

When building WebKitGTK+, it’s a good idea to stick to the default values for the build options. If you’re building some sort of embedded system and really know what you’re doing, then OK, it might make sense to change some settings and disable some stuff. But Linux distros are generally well-advised to stick to the defaults to avoid creating problems for users.

One exception is if you need to disable certain features to avoid newer dependencies when building WebKit for older systems. For example, Ubuntu 18.04 disables web fonts (ENABLE_WOFF2=OFF) because it doesn’t have the libbrotli and libwoff2 dependencies that are required for that feature to work, hence some webpages will display using subpar fonts. And distributions shipping older versions of GStreamer will need to disable the ENABLE_MEDIA_SOURCE option (which is missing from the below feature list by mistake), since that requires the very latest GStreamer to work.

Other exceptions are the ENABLE_GTKDOC and ENABLE_MINIBROWSER settings, which distros do want. ENABLE_GTKDOC is disabled by default because it’s slow to build, and ENABLE_MINIBROWSER because, well, actually I don’t know why, you always want that one and it’s just annoying to find it’s not built.

OK, but really now, other than those exceptions, you should probably leave the defaults alone.

The feature list that prints when building WebKitGTK+ looks like this:

--  ENABLE_DRAG_SUPPORT                     ON
--  ENABLE_GEOLOCATION .................... ON
--  ENABLE_GLES2                            OFF
--  ENABLE_GTKDOC ......................... OFF
--  ENABLE_ICONDATABASE                     ON
--  ENABLE_INTROSPECTION .................. ON
--  ENABLE_JIT                              ON
--  ENABLE_MINIBROWSER .................... OFF
--  ENABLE_OPENGL                           ON
--  ENABLE_QUARTZ_TARGET                    OFF
--  ENABLE_SPELLCHECK                       ON
--  ENABLE_TOUCH_EVENTS ................... ON
--  ENABLE_VIDEO                            ON
--  ENABLE_WAYLAND_TARGET ................. ON
--  ENABLE_WEBDRIVER                        ON
--  ENABLE_WEB_AUDIO ...................... ON
--  ENABLE_WEB_CRYPTO                       ON
--  ENABLE_X11_TARGET ..................... ON
--  USE_LIBHYPHEN                           ON
--  USE_LIBNOTIFY ......................... ON
--  USE_LIBSECRET                           ON
--  USE_SYSTEM_MALLOC ..................... OFF
--  USE_WOFF2                               ON

And, asides from the exceptions noted above, those are probably the options you want to ship with.

Why are some things disabled by default? ENABLE_ACCELERATED_2D_CANVAS is OFF by default because it is experimental (i.e. not great :) and requires CairoGL, which has been available in most distributions for about half a decade now, but still hasn’t reached Debian yet, because the Debian developers know that the Cairo developers consider CarioGL experimental (i.e. not great!). Many of our developers use Debian, and we’re not keen on having two separate sets of canvas bugs depending on whether you’re using Debian or not, so best keep this off for now. ENABLE_GLES2 switches you from desktop GL to GLES, which is maybe needed for embedded systems with crap proprietary graphics drivers, but certainly not what you want when building for a general-purpose distribution with mesa. Then ENABLE_QUARTZ_TARGET is for building on macOS, not for Linux. And then we come to USE_SYSTEM_MALLOC.

USE_SYSTEM_MALLOC disables WebKit’s bmalloc memory allocator (“fast malloc”) in favor of glibc malloc. bmalloc is performance-optimized for macOS, and I’m uncertain how its performance compares to glibc malloc on Linux. Doesn’t matter really, because bmalloc contains important heap security features that will be disabled if you switch to glibc malloc, and that’s all you need to know to decide which one to use. If you disable bmalloc, you lose the Gigacage, isolated heaps, heap subspaces, etc. I don’t pretend to understand how any of those things work, so I’ll just refer you to this explanation by Sam Brown, who sounds like he knows what he’s talking about. The point is that, if an attacker has found a memory vulnerability in WebKit, these heap security features make it much harder to exploit and take control of users’ computers, and you don’t want them turned off.

USE_SYSTEM_MALLOC is currently enabled (bad!) in openSUSE and SUSE Linux Enterprise 15, presumably because when the Gigacage was originally introduced, it crashed immediately for users who set address space (virtual memory allocation) limits. Gigacage works by allocating a huge address space to reduce the chances that an attacker can find pointers within that space, similar to ASLR, so limiting the size of the address space prevents Gigacage from working. At first we thought it made more sense to crash than to allow a security feature to silently fail, but we got a bunch of complaints from users who use ulimit to limit the address space used by processes, and also from users who disable overcommit (which is required for Gigacage to allocate ludicrous amounts of address space), and so nowadays we just silently disable Gigacage instead if enough address space for it cannot be allocated. So hopefully there’s no longer any reason to disable this important security feature at build time! Distributions should be building with the default USE_SYSTEM_MALLOC=OFF.

The openSUSE CMake line currently looks like this:

%cmake \
  -DLIBEXEC_INSTALL_DIR=%{_libexecdir}/libwebkit2gtk%{_wk2sover} \
%if 0%{?suse_version} == 1315
%if 0%{?suse_version} <= 1500
  -DUSE_WOFF2=false \
%if %{with python3}
  -DPYTHON_EXECUTABLE=%{_bindir}/python3 \
%if !0%{?is_opensuse}
%ifarch armv6hl ppc ppc64 ppc64le riscv64 s390 s390x
  -DCMAKE_EXE_LINKER_FLAGS="-Wl,--as-needed -Wl,-z,now -pthread" \
  -DCMAKE_MODULE_LINKER_FLAGS="-Wl,--as-needed -Wl,-z,now -pthread" \
  -DCMAKE_SHARED_LINKER_FLAGS="-Wl,--as-needed -Wl,-z,now -pthread"

which all looks pretty reasonable to me: certain features that require “newer” dependencies are disabled on the old distros, and NPAPI plugins are not supported in the enterprise distro, and JIT doesn’t work on odd architectures. I would remove the ENABLE_JIT=OFF lines only because WebKit’s build system should be smart enough nowadays to disable it automatically to save you the trouble of thinking about which architectures the JIT works on. And I would also remove the -DUSE_SYSTEM_MALLOC=ON line to ensure users are properly protected.

By Michael Catanzaro at November 03, 2018 03:29 AM

October 24, 2018

Release Notes for Safari Technology Preview 68

Surfin’ Safari

Safari Technology Preview Release 68 is now available for download for macOS Mojave and macOS High Sierra. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS Mojave and from the Mac App Store’s Updates tab on macOS High Sierra. After updating to macOS Mojave, you may have to reinstall Safari Technology Preview.

This release covers WebKit revisions 236793-237231.


  • Enabled <input type="color"> support (r236942)
  • Fixed the Document and Window objects to lose their browsing context as soon as its iframe is removed from the document (r236862)
  • Fixed incorrect input.checked when parsing its children (r236795)
  • Fixed window.navigator and window.performance to not become null after the window loses its browsing context (r237185, r237209)
  • Changed to restrict browsing context lookup by name to frames that are related to one another (r237112)
  • Changed anchor target to be ignored on activation when the download attribute is set (r236987)
  • Changed target="_blank" on anchors to imply rel="noopener" (r237144)
  • Fixed incorrect garbage collection of JavaScript node wrappers held by MutationObserver and MutationRecord (r236850, r236801)


  • Added VP8 support to WebRTC (r236821)
  • Added support for IceCandidate stats (r236963)
  • Added support for reporting “display composited video frames” through the VideoPlaybackQuality object (r236875)
  • Added support for RTCPeerConnection.generateCertificate (r237140)
  • Added support for RTCConfiguration.certificates (r237202)
  • Implemented error handler of MediaRecorder (r237106)


  • Added support for inline WebVTT styles (r237187)
  • Changed to use nanoseconds as MaximumTimeScale (r237208)
  • Changed to only report the supported WebGL version (r237018)


  • Added prefers-color-scheme media query support for styling dark mode content (r237156)
  • Changed to resolve inset properties to computed style when there is over-constrainment (r236979)


  • Fixed slow tiling for CSS gradients (r237230)


  • Added BigInt support for the bitwise | operator (r236901)

Web Inspector

  • Added the ability to go directly from an event in the overview view to the specialized timeline for that event (r237195)
  • Added support for showing redirect requests in the Network and Timelines tabs (r236995)
  • Added table support for multiple selection and ⌘ Click (Command-Click) behavior (r236853)
  • Changed to use the iframe name attribute for FrameTreeElement (r236885)
  • Changed to allow multiple canvases to be recorded at the same time (r236952)
  • Created a special Network waterfall for media events (r237028)
  • Exposed Server Timing response headers in the Network tab (r237151)
  • Fixed the Canvas recording sidebar scroll position after switching tabs (r237196)
  • Fixed the color contrast of the disabled Record button in the Canvas tab (r236986)
  • Fixed capturing previously saved states and adding them to the recording payload in the Canvas tab (r237198)
  • Fixed previews to be removed when the parent view is hidden in the Canvas tab (r237090)
  • Fixed clicking the initiator link in the Network tab table to automatically switch to the Preview section (r236923)
  • Fixed dark mode contrast issues (r236953, r237085, r237150)
  • Fixed style editor warnings to not look like errors in dark mode (r237125)
  • Fixed unreadable text when hovering over CSS properties while holding the ⌘ (Command) key in dark mode (r237143)
  • Fixed the “goto arrow” color for the selected DOM breakpoint tree element in dark mode (r237078)
  • Fixed the detail view to be correctly shown after sorting the Network table (r237043)
  • Fixed the detail view reverting to “Response” when new requests are added in the Network tab (r237061)
  • Fixed the Open Resource dialog to show the path to the resource to disambiguate resources with the same name (r236918)
  • Fixed the toolbar getting hidden when Web Inspector is docked to side (r237131)
  • Fixed ⌃G (Control-G) to not wipe the line when jumping to the line in a CSS file (r237212)
  • Grouped media network entries by the node that triggered the request (r236927)
  • Indented all network entries when “Group by Node” is enabled (r237006)


  • Fixed a bug where some key combinations such as ⌘A (Command-A) can cause the WebDriver session to hang (r236939)
  • Fixed a crash when a WebDriver session is terminated while waiting for simulated inputs to be handled (r236852)
  • Fixed a hang when creating a WebDriver session for Safari Technology Preview (macOS Mojave only).

Payment Request

  • Changed to abort requests after details settle when the user cancels (r236922)

Apple Pay

  • Fixed new shipping methods getting ignored when updating after the shippingaddresschange event (r237142)
  • Changed payment authorization results with ApplePayErrors to never be considered final (r237134)

Web Animations

  • Fixed setting animation-name:none after a fill:forwards animation has completed to correctly revert to the unanimated style (r236809)


  • Changed ECDSA to be able to handle invalid signature inputs (r236820)

October 24, 2018 05:00 PM

October 20, 2018

Manuel Rego: Igalia at TPAC 2018

Igalia WebKit

Just a quick update before boarding to Lyon for TPAC 2018. This year 12 igalians will be at TPAC, 10 employees (Álex García Castro, Daniel Ehrenberg, Javier Fernández, Joanmarie Diggs, Martin Robinson, Rob Buis, Sergio Villar, Thibault Saunier and myself) and 2 coding experience students (Oriol Brufau and Sven Sauleau). We will represent Igalia in the different working groups and breakout sessions.

On top of that Igalia will have a booth in the solutions showcase where we’ll have a few demos of our last developments like: WebRTC, MSE, CSS Grid Layout, CSS Box Alignment, MathML, etc. Showing them in some low-end boards like the Raspebrry Pi using WPE an optimized WebKit port for embedded platforms.

Thread by W3C Developers announcing my talk.

In my personal case I’ll be attending the CSS Working Group (CSSWG) and Houdini Task Force meetings to follow the work Igalia has been doing on the implementation of different standards. In addition, I’ll be giving a talk about how to contribute to the evolution of CSS on the W3C Developer Meetup that happens on Monday. I’ll try to explain how easy is nowadays to provide feedback to the CSSWG and have some influence on the different specifications.

Tweet by Daniel Ehrenberg about the Web Platform position.

Last but not least, Igalia Web Platform Team is hiring, we’re looking for people willing to work on web standards from the implementation on the different browser engines, to the discussions with the standard bodies or the definition of test suites. If you’re attending TPAC and you want to work on a flat company focused on free software development, probably you are a good candidate to join us. Read the position announcement and don’t hesitate to talk to any of us there about that.

See you at TPAC tomorrow!

October 20, 2018 10:00 PM

October 15, 2018

Canvas Debugging

Surfin’ Safari

Ever since its introduction in 2004, the Canvas element and its associated APIs have been an incredible tool for generating specific visual effects on a webpage. As more technologies, such as WebGL, came into being, Canvas’ complexity grew, and more was expected of the developer. For many years, debugging Canvas issues was a process of adding console.log statements, or even overriding the prototype of the Canvas’ context to better understand when functions are being called. Today, we’re excited to tell you about our improvements to the debugging process for Canvas, specifically the ways in which we are providing in-depth insight into the cause and effect of every action, as well as exposing in-process information that was previously invisible.

Canvas Tab

Web Inspector now has a dedicated Canvas tab for debugging canvas contexts. This new tool makes it easier to diagnose performance and correctness problems in canvas drawing code without having to manually instrumenting your code. The rest of this post explains these new capabilities.

Visualizing Canvases

The Canvas tab overview shows all active canvas contexts, listing the type of drawing context, preview image, dimensions, and current memory usage for each canvas in the page.

Canvas Tab

At any point, clicking on the refresh button in the top right of either the “card” or the Canvas tab will refresh the preview image(s) so that you can stay up to date on what you are looking at from the page.

Clicking on any Canvas will “drill down” into a more specific view, where any attached objects, such as Shader Programs, can be viewed and edited.

Canvas View

Recording and Replaying Canvases

A big part of the Canvas debugging initiative was to provide a near-native exploration of exactly what happens to the Canvas. It’s often difficult to debug drawing code because so much of it occurs behind the scenes, as only a few actions actually cause changes (if any) to be drawn. 2D and WebGL canvases are now able to be recorded and visualized action-by-action as needed to debug any issues. Clicking the red circle next to the canvas preview (overview) or in the left sidebar (specific canvas) will start a recording. When you’ve reproduced the behavior you want to debug, click the button again to stop recording. It is also possible to take single-frame recordings by holding Shift when clicking. After some processing, the recording will become available for inspection.

Recording View

The recording view shows a list of all commands (left sidebar), the current state and backtrace (right sidebar), and the current output up to the selected command (center). Clicking on any action will apply it and everything prior to the preview, generating the same result as the one viewed in the actual page. Moving the slider will quickly jump between “visual” actions (highlighted in the left sidebar), which are those that can cause a visible change in the generated content.

Debugging 2D Paths

In the 2D Canvas world, there exists a concept called “path”. To give an analogy, imagine a painter using a pencil to sketch out a brush stroke before actually painting. For 2D Canvas, the “path” is this penciled line that can be used to draw more expressive shapes all in one go. Normally, like the pencil, this path is invisible until actually drawn/painted. This can lead to unintended results if the developer put the wrong value by accident.

Recording Path

Dashed lines represent any “move” commands. The most recent path action is drawn in red.

Export and Import

One problem we envisioned while building Canvas Recording was that a recording is only as good as what it was able to capture. If a developer encounters a bug on their computer, but their coworker doesn’t have an issue, then there’s no real benefit to being able to record the buggy Canvas, especially if they don’t know how the code works. Our solution is to make Canvas Recording fully portable by allowing any recording to be exported to a JSON file and imported into any other computer.

All of the recording information is encoded into the JSON file, so loading it into any other computer will provide the exact same replay accuracy as on the origin computer. In order to minimize the size of a Canvas Recording, however, values are deduplicated and repeated keys are removed in favor of more compact arrays. According to our rough estimates, this decreased the average JSON size by about 30%.

Shader Program Editor

For more advanced Canvas usage, such as WebGL, it is often the case that much of the work is done in a Shader. In these cases, recording the Canvas might not be enough to determine the cause of a potential problem, as it might be due to an error in one of the Shaders used by the Canvas. In order to facilitate this, we have exposed all valid Shader Programs for the selected Canvas.

The original source of the Shader Program is shown in a split view for the Vertex and Fragment shaders. Each of these is editable, and will have an immediate effect on the inspected page.

In this way, bugs can be ironed out without having to edit the source of the page, or having to take additional recordings.


As a simple demo for debugging using Canvas Recording, this page is the one displayed in the screenshots above. It heavily utilizes canvas 2D paths, often times outside the bounds of the canvas. This is a good example of a time to optimize, as there’s no reason to draw something outside the visible space. Thanks to Canvas Recording, this issue is very apparent and has enough information to make a fix actionable.


The Canvas tab is available in macOS High Sierra 10.13.4 and macOS Mojave. Is there a Canvas API that wasn’t covered here that you debug often? Let us know! Please feel free to send us feedback on Twitter (@jonathandavis) or by filing a bug.

October 15, 2018 05:00 PM

Deprecation of Legacy TLS 1.0 and 1.1 Versions

Surfin’ Safari

Transport Layer Security (TLS) is a critical security protocol used to protect web traffic. It provides confidentiality and integrity of data in transit between clients and servers exchanging (often sensitive) information. To best safeguard this data, it is important to use modern and more secure versions of this protocol. Specifically, applications should move away from TLS 1.0 and 1.1. Doing so provides many benefits, including:

  • Modern cryptographic cipher suites and algorithms with desirable performance and security properties, e.g., perfect forward secrecy and authenticated encryption, that are not vulnerable to attacks such as BEAST.
  • Removal of mandatory and insecure SHA-1 and MD5 hash functions as part of peer authentication.
  • Resistance to downgrade-related attacks such as LogJam and FREAK.

Now is the time to make this transition. Properly configured for App Transport Security (ATS) compliance, TLS 1.2 offers security fit for the modern web. It is the standard on Apple platforms and represents 99.6% of TLS connections made from Safari. TLS 1.0 and 1.1 — which date back to 1999 — account for less than 0.36% of all connections. With the recent finalization of TLS 1.3 by the IETF in August 2018, the proportion of legacy TLS connections will likely drop even further. TLS 1.2 is also required for HTTP/2, which delivers significant performance improvements for the web.

Therefore, we are deprecating support for TLS 1.0 and 1.1. Complete support will be removed from Safari in updates to Apple iOS and macOS beginning in March 2020. Firefox, Chrome, and Edge are also planning to drop TLS 1.0 and 1.1 support at that time. If you own or operate a web server that does not support TLS 1.2 or newer, please upgrade now. If you use legacy services or devices that cannot be upgraded, please let us know by contacting our Web Technologies Evangelist or by filing a bug report with details.

October 15, 2018 04:00 PM

October 12, 2018

MotionMark 1.1

Surfin’ Safari

Two years ago, we released MotionMark, a benchmark for Web graphics. It runs a series of tests that exercise common ways of painting on the Web. We’ve used this benchmark to improve the performance of WebKit and underlying frameworks, and we’re happy to see that others have used the benchmark for their own performance investigations.

Today we are announcing an update to the MotionMark benchmark, which we’re calling version 1.1.

Test updates

First, let’s do a quick review about the benchmark. MotionMark runs a suite of tests that measures a browser’s painting performance by exercising various techniques, including CSS, text, canvas, and SVG. Each test packages a small set of graphics primitives into a single rendering element, and renders as many of them as possible while maintaining 60 fps. That number represents the test’s score. For more details, you can read our introductory blog post.

We want to expose MotionMark to as many aspects of the rendering engine as possible. In our first update to the benchmark, we’ve refreshed two tests in the suite.

The presentation of the Multiply test, which utilizes DOM element painting, caps the maximum number of elements that can be drawn. MotionMark requires tests to be able to stress browsers such that they cannot maintain 60 fps, and some of Apple’s new hardware, like the iPhone Xs, were powerful enough to animate Multiply at the maximum complexity at 60 fps. So we had to make the test harder! We reduced the physical size of each element to fit more of them on the available space and increase that cap threefold. We also updated the ways that an element can be hidden during the test. Before the elements toggled their visibility using visibility: hidden; now they also do so via display: none and opacity: 0.

In the original 1.0 suite, each rendering element in the Leaves test was an image to which translate and rotate transforms were applied. For 1.1 we use the width and height attributes to paint the images in a range of different sizes, and test blending by animating a fade using opacity.

Leveraging MotionMark’s design for easier analysis

MotionMark has enabled us to monitor our graphics performance in WebKit and underlying system frameworks we depend on like CoreAnimation, as well as find opportunities to progress performance. As our experience in regression analysis with this benchmark grew, we found a couple of processes that facilitated our efforts to isolate bottlenecks and verify performance gains.

First, we split tests from the “main” suite into derivative versions based on specific techniques. For example, with the Multiply test update mentioned earlier, we created versions where all of the elements used only one of the CSS techniques for hiding an element. For the Design test we created a version that only contained Latin text, one that used East Asian characters, and one that used right-to-left and complex scripts. Isolating the techniques made it easier to determine which part of the test WebKit regressed, and magnified problems in traces for easier analysis.

Second, we added a way to run a test more simply, with a fixed number of elements. The benchmark uses a ramping controller that varies the painting load such that it repeatedly crosses over the threshold where the browser can no longer render the scene at 60 fps. Analyzing Instruments traces for such a run can be difficult to track a regression, however, since the load is dynamic from frame to frame. MotionMark’s design allows us to plug in different kinds of controllers, and using one that simply rendered a scene at a static complexity facilitated A/B analyses across versions of WebKit and the OS. Subsequent fixes could then be easily verified using both the fixed and ramping controllers.


Using MotionMark as a tool for tracking regressions and discovering ways to progress have been critical for us to improve graphics performance in WebKit. As a result, we’ve made Safari on macOS Mojave and iOS 12 on average over 20% faster on MotionMark 1.1 than in the previous release.

MotionMark 1.1 Results

In conclusion, MotionMark has been updated to version 1.1 to scale better on faster hardware and include more techniques for painting. We hope this benchmark continues to be a useful tool for browsers to optimize their engines for the modern Web.

October 12, 2018 05:00 PM

October 10, 2018

Viewing Augmented Reality Assets in Safari for iOS

Surfin’ Safari

Safari on iOS 12 supports viewing 3D models and allows you to see them in Augmented Reality (AR). Supported assets use the Universal Scene Description format, or USDZ, developed by Pixar.

Apple has made a gallery of examples for you to play with. This post will tell you how to author Web content to reference USDZ files so your users can experience AR.

Serving USDZ content

For Safari to recognize AR content it must be served over HTTP with the appropriate MIME-type. Safari is looking for model/vnd.pixar.usd.

Since this is a new format, it’s unlikely that your Web server knows about USDZ. You may need to configure it to serve the appropriate header. For Apache, the configuration would look something like this:

AddType model/vnd.pixar.usd usdz # All files ending in .usdz served as USD.

Refer to your Web server documentation, or your Web Application Framework documentation, for information on how to set the Content-Type header.

Note that the official MIME-type for USDZ was recently registered as model/vnd.usdz+zip. At the moment Safari does not recognize that type, but this post will be updated when it does.

Linking to USDZ

Once the content is served with the correct MIME-type, you can link to USDZ content in the normal manner.

<a href="heart-tapback.usdz">iMessage Heart Tap-back</a>

Here is such a link: iMessage Heart Tap-back

Upon tapping that link, Safari on iOS will navigate to a page that shows a static thumbnail of the 3D asset. Tapping again on the thumbnail will open a live view where the user can pan and zoom, and switch into AR mode. Any animations embedded in the USDZ will play in the live view. The user can exit that view and then return to the previous page using the back button.

In this way, linking to a USDZ file is just like linking to other files.

In-place viewing of USDZ

Navigating away from a page to get an AR experience might be disruptive to your interaction. There is a better way to show AR content by marking-up the link element in such a way that Safari knows in advance how the link should be processed.

By adding rel="ar" to your a (link/anchor) element, Safari won’t navigate on tap. Instead it will jump directly into the live 3D view and, upon exit, returns to your page.

Safari decorates such links with a 3D-cube badge in the top-right corner, to show the user there is an AR experience. You may have noticed this experience on the gallery mentioned earlier.
There are some extra requirements for the link. We already mentioned the rel attribute. The link must also contain a single child that is either an img or picture element. For example:

<a rel="ar" href="model.usdz">
    <img src="model-preview.jpg">

Obviously you can use whatever image you like inside the anchor.

Feature Detection

To detect support for AR, you can use the following JavaScript:

const a = document.createElement("a");
if (a.relList.supports("ar")) {
  // AR is available.

Other than Safari, the AR integration is available in SFSafariViewController clients. We’ve also received requests to add it to WKWebView.

More information on iOS and AR can be found in WWDC 2018 Session 603 – Integrating Apps and Content with AR Quick Look. The section relevant to Safari begins about 16 minutes in. Other parts of that session discuss creating USDZ files. General documentation on Apple’s AR frameworks is available from the developer site.

October 10, 2018 06:00 PM

Release Notes for Safari Technology Preview 67

Surfin’ Safari

Safari Technology Preview Release 67 is now available for download for macOS Mojave and macOS High Sierra. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS Mojave and from the Mac App Store’s Updates tab on macOS High Sierra. After updating to macOS Mojave, you may have to reinstall Safari Technology Preview.

This release covers WebKit revisions 236195-236793.

Pointer Events

  • Added PointerEvent in the Experimental Features menu (r236378)
  • Ensured PointerEvent is not visible when disabled (r236410)


  • Added RTCCodecStats support (r236346)
  • Changed to allow IP mismatch for local connections on localhost (r236316)
  • Cleaned up change handling for RealtimeMediaSource settings (r236646)
  • Fixed video track clone to preserve original property (r236536)
  • Implemented sender and receiver getStats (r236207)
  • Updated constraints supported by getDisplayMedia (r236476)


  • Enabled H.264 Simulcast (r236792)
  • Enabled Modern Encrypted Media API by default in the Experimental Features menu (r236281)
  • Added WebM sanitization in EME (r236256, r236307)
  • Introduced the concept of CDMInstanceSession for EME (r236317)
  • Changed to use some tolerance when deciding whether a frame should be appended to the decode queue in MSE (r236258)
  • Fixed a comparison with an uninitialized greatestDecodeDuration in MSE (r236314)
  • Fixed an unwanted erased sample from the decode queue in MSE (r236566)
  • Fixed WebVTT cue alignment (r236531)
  • Updated the WebVTT parser according to new region syntax (r236265)


  • Fixed item alignment next to collapsed tracks with gutters in CSS Grid (r236643)
  • Restricted the total combined size of backdrop filters (r236306)
  • Fixed CSS reference filter with feDisplacementMap buffer corruption on Retina displays (r236415)
  • Fixed updating feMorphology filter in CSS when the element moves (r236416)
  • Fixed a garbled rendering of an image when feConvolveMatrix is applied to it on a Retina display (r236412)
  • Started implementing CSS Custom Properties and Values (r236273)
  • Implemented initialValue support for CSS Custom Properties and Values API (r236379)
  • Made overflow:overlay a synonym for overflow:auto (r236341)
  • Fixed <form> in quirks mode to have margin-block-end:1em (r236673)


  • Implemented BigInt support for bitwise & operation (r236637)
  • Optimized Array#indexOf in the C++ runtime (r236240)
  • Optimized Array#lastIndexOf in the C++ runtime (r236496)

Web Animations

  • Fixed accelerated animations to get suspended (r236312, r236313)
  • Fixed endlessly calling DocumentTimeline::updateAnimations() (r236308)
  • Ensured renderers with accelerated animations have layers (r236501, r236670)

Shadow DOM

  • Added the support for users to select content across shadow boundaries (r236519)
  • Added the support for copying content across shadow boundaries (r236785)


  • Fixed custom elements in a reaction queue losing its JavaScript wrapper and becoming an HTMLUnknownElement (r236376)
  • Fixed elements enqueued in mutation observers losing its JavaScript wrappers (r236519)
  • Changed Image.proto to be a Function.prototype not an HTMLElement.prototype (r236769)
  • Fixed radio inputs and checkbox inputs to fire “click”, “input”, and “change” events in order when clicked (r236779)
  • Simplified authentication code (r236344)
  • Changed to not propagate URLs to non-fully active documents (r236550)
  • Changed to throw errors for cross-origin calls (r236613)
  • Changed to strip the fragment from the document URL during URL propagation (r236560)
  • Fixed no-op calls to ensure no side effects (r236433)
  • Dropped support for the cross-origin-window-policy header (r236623)

Apple Pay

  • Added support for granular errors in PaymentDetailsUpdate (r236552)
  • Removed the “in-store” button type (r236615)

Web Inspector

  • Fixed an issue that caused Web Inspector’s tabs to be hidden when docked to the side (r236411)
  • Fixed an issue that caused dock buttons to disappear when Web Inspector goes fullscreen (r236375)
  • The Debugger tab now has one unified section for all breakpoint types (r236540)
  • Fixed the light background on new watch expression popover in Dark Mode (r236532)
  • Fixed image resources without content getting shown when the Images folder is selected (r236596)
  • Removed the Legacy Style Editor (r236336)
  • Removed the Visual Style CSS details sidebar panel (r236298)
  • Reworked the Computed panel in the Styles sidebar panel to match the styles of the Rules panel (r236297)
  • Added an experimental setting for multi-property selection (r236706)
  • Changed to start editing property names and values on mouseup instead of mousedown in the Styles sidebar (r236780)

Web Driver

  • Fixed an issue wherein sending a Tab key press could sometimes shift focus out of web content and hang the WebDriver session (r236774)
  • Fixed an issue that caused safaridriver to immediately abort on launch
  • Fixed an issue where the Perform Actions command failed if a keyboard input source specified a tick containing a “pause” value without a “key” value


  • Fixed an WebSQL issue preventing the user from granting a quota increase if the JavaScript provides an expected usage value that is too low (r236348)

October 10, 2018 05:00 PM

October 09, 2018

Manuel Rego: Web Engines Hackfest 2018

Igalia WebKit

One year more and a new edition of the Web Engines Hackfest was arranged by Igalia. This time it was the tenth edition, the first five ones using the WebKitGTK+ Hackfest name and another five editions with the new broader name Web Engines Hackfest. A group of igalians, including myself, have been organizing this event. It has been some busy days for us, but we hope everyone enjoyed it and had a great time during the hackfest.

This was the biggest edition ever, we were 70 people from 15 different companies including Apple, Google and Mozilla (three of the main browser vendors). It seems the hackfest is getting more popular, several people attending are repeating in the next editions, so that shows they enjoy it. This is really awesome and we’re thrilled about the future of this event.


The presentations are not the main part of the event, but I think it’s worth to do a quick recap about the ones we had this year:

  • Behdad Esfahbod and Dominik Röttsches from Google talked about Variable Fonts and the implementation in Chromium. It’s always amazing to check the possibilities of this new technology.

  • Camille Lamy, Colin Blundell and Robert Kroeger from Google presented the Servicification effort in the Chromium project. Which is trying to modularize Chromium in smaller parts.

  • Žan Doberšek from Igalia gave an update on WPE WebKit. The port is now official and it’s used everyday in more and more low-end devices.

  • Thibault Saunier from Igalia complemented Žan’s presentation talking about the GStreamer based WebRTC implementation in WebKitGTK+ and WPE ports. Really cool to see WebRTC arriving to more browsers and web engines.

  • Antonio Gomes and Jeongeun Kim from Igalia explained the status of Chromium on Wayland and it’s way to become fully supported upstream. This work will help to use Chromium on embedded systems.

  • Youenn Fablet from Apple closed the event talking about Service Workers support on WebKit. This is a key technology for Progressive Web Apps (PWA) and is now available in all major browsers.

The slides of the talks are available on the website and wiki. The videos will be published soon in our YouTube channel.

Some pictures from Web Engines Hackfest 2018 Some pictures from Web Engines Hackfest 2018 (Flickr album)

Other topics

During the event there were breakout sessions about many different topics. In this section I’m going to talk about the ones I’m more interested on.

  • Web Platform Tests (WPT)

    This is a key topic to improve interoperability on the web platform. Simon Pieters started the session with an introduction to WPT just in case someone was not aware of the repository and how it works. For the rest of the session we discussed the status of WPT on the different browsers.

    Chromium and Firefox are doing an automatic two ways (import/export) synchronization process so the tests can be easily shared between both implementations. On the other side WebKit still has some kind of manual process over the table, neither import or export is totally automatic, there are some scripts that help with the process though.

    Apart from that, WPT is a first-class citizen in Chromium, and the encouraged way to do new developments. In Firefox it’s still not there, as the test suites are not run in all the possible configurations yet (but they’re getting there).

    Finally the WPT dashboard is showing results for the most recent unstable releases of the different browsers, which is really cool despite being somehow hidden on the UI:

  • LayoutNG

    Christian Biesinger gave an introduction to LayoutNG project in Blink, where Google is rewriting Chromium’s layout engine. He showed the main ideas and concepts behind this effort and navigated the code showing some examples. According to Christian things are getting ready and LayoutNG could be shipping in the coming months for inline and block layout.

    On top of questions about LayoutNG, we briefly mentioned how other browsers are also trying to improve the layout code: Firefox with Servo layout and WebKit with Layout Formatting Context (LFC) aka Layout Reloaded. It seems quite clear that the current layout engines are getting to their limits and people are looking for new solutions.

  • Chromium downstream

    Several companies (Google included) have to maintain downstream forks Chromium with their own customizations to fit their particular use cases and hardware platforms.

    Colin Blundell was explaining how it was the process of maintaining the downstream version of Chrome for iOS. After trying many different strategies the best solution was rebasing their changes 2-3 times per day. That way the conflicts they had to deal with were much simpler to resolve, otherwise it was not possible for them to cope with all the upstream changes. Note that he mentioned that one (rotatory) full-time resource was required to perform this job in time.

    It was good to share the experiences of different companies that are facing very similar issues for this kind of work.

Thank you very much

Just to close this post, big thanks to all the people attending the event, without you the hackfest wouldn’t have any sense at all. People are key for this event where discussions and conversations are one of the main parts of it.

Of course special acknowledgments to the speakers for the hard work they put on their lovely talks.

Finally I couldn’t forget to thank the Web Engines Hackfest 2018 sponsors: Google and Igalia. Without their support this event won’t be possible.

Web Engines Hackfest 2018 sponsors: Google and Igalia Web Engines Hackfest 2018 sponsors: Google and Igalia

Looking forward for a new edition!

October 09, 2018 10:00 PM

September 26, 2018

Release Notes for Safari Technology Preview 66

Surfin’ Safari

Safari Technology Preview Release 66 is now available for download for macOS Mojave and macOS High Sierra. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS Mojave and from the Mac App Store’s Updates tab on macOS High Sierra. After updating to macOS Mojave, you may have to reinstall Safari Technology Preview.

This release covers WebKit revisions 235669-236195.

This release of Safari Technology Preview has a known issue where launching SafariDriver fails.

Web Share API

  • Implemented the Web Share API (r235925)

Conic Gradients

  • Added support for Conic Gradients (r235772)
  • Fixed angle interpretation for Conic Gradients (r235868)
  • Fixed color stop blending in Conic Gradients for stops past the first stop (r235999)


  • Enabled WebRTC Unified Plan as an Experimental Feature (r236144)
  • Exposed RTCRtpSender.setParameters (r235714)
  • Introduced a backend for RTCRtpTransceiver (r235719)

Shadow DOM

  • Fixed :first-child, :last-child, :nth-child, and :nth-of-type to work on shadow root’s children (r235917)
  • Fixed mouseenter and mouseleave events to get dispatched when there is a capturing event listener for a slot ancestor (r235865)


  • Added support for double-position gradient color stop syntax (r236155)

Web Inspector

  • Updated the bezier curve editor for Dark Mode (r235998)
  • Changed to generate CSSKeywordCompletions from backend values (r236091)
  • Fixed imported recordings that are unable to be viewed after navigation (r235937)
  • Fixed opening Web Inspector with a selected element that might immediately scroll that element off screen in the DOM Tree outline (r235996)
  • Changed to record actions performed on ImageBitmapRenderingContext (r236008)
  • Fixed Source View to scroll to show the line when a breakpoint is hit inside of a <script> in an HTML resource (r236028)
  • Fixed a Location popover triggering for a hidden Location column when clicking a row in the Script Events grid of the Timelines tab (r235997)


  • Fixed XMLHttpRequest open() to throw a SYNTAX_ERR exception if the method is empty or the URL cannot be resolved (r235808)
  • Fixed overrideMimeType to not update the Content-Type header in the XMLHttpRequest response (r235844)

Apple Pay

  • Updated to dispatch a paymentmethodchange event when the payment method changes (r235833)
  • Renamed the -apple-pay-button-type value checkout to check-out (r235754)


  • Fixed Symbol.prototype.description to handle a null Symbol (r235712)


  • Added Media Capabilities API as an Experimental Feature (r235675)
  • Added support for HEVC codec types in Media Capabilities (r236094)
  • Fixed track.onmute not getting called for a remote MediaStreamTrack when its counter part track is removed from the peer connection (r236090)
  • Updated to include supported frame rates in video capture presets (r235760)
  • Simplified logic when changing RealtimeMediaSource settings (r235670)
  • Changed the middle value to center in WebVTT for consistency with CSS (r236143)

Web Animations

  • Fixed a failure that occurred when interrupting an accelerated CSS transition on a composited element in-flight (r235843)
  • Fixed accelerated animations to correctly respect positive delay values (r235854, r236072)

Web Assembly

  • Optimized JavaScript to Web Assembly call by removing Vector allocation (r235778)

Password AutoFill

  • Automatically submit login forms when filling credentials with Password AutoFill
  • On MacBook Pro with Touch Bar, require authentication with Touch ID to fill passwords into web pages; this can be changed in Safari’s AutoFill preferences

September 26, 2018 05:00 PM

September 10, 2018

Release Notes for Safari Technology Preview 65

Surfin’ Safari

Safari Technology Preview Release 65 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 235171-235669.

Storage Access API

  • Made a change to maintain access through same-site navigations of an iframe (r235569)
  • Updated the Storage Access API prompt to show the eTLD+1s, not the full host names (r235209)


  • Fixed scrubbing video with Touch Bar on YouTube to prevent video playback freezing (r235334)
  • Fixed muted elements not updating their Now Playing status when unmuted (r235474)

Apple Pay

  • Added Web Inspector auto-complete keywords for -apple-pay-button-style and -apple-pay-button-type (r235406)
  • Changed to allow $0 totals (r235318)
  • Changed to reject when an unsupported ApplePayRequest version is specified (r235342)
  • Introduced Apple Pay JS v4 (r235251)
  • Introduced new values for -apple-pay-button-type (r235349)

Payment Request

  • Added an onpayerdetailchange event handler to PaymentResponse (r235625)
  • Implemented the MerchantValidationEvent constructor (r235600)
  • Removed PaymentAddress.languageCode (r235607)

Shadow DOM

  • Changed to compose click events from click() (r235337)
  • Fixed the focus navigation order in slot fallback contents (r235191)

Fetch API

  • Made a change to stop checking the Request.integrity value in no-CORS mode (r235174)

Service Workers

  • Fixed undefined self.isSecureContext in Service Workers (r235234)


  • Added getModifierState to MouseEvent (r235329)

Web Inspector

  • Added auto-completion for event breakpoints (r235389)
  • Added support for breakpoints for timers and animation-frame events (r235248)
  • Fixed deleting multiple event breakpoints by repeatedly hitting delete (r235183)
  • Fixed the color picker to allow entering decimal numbers for opacity (r235273)
  • Fixed typos in some compositing reasons (r235257)
  • Fixed the Search bar being too narrow in some localizations (r235447)
  • Fixed console.inspect(sessionStorage) to correctly show the Session Storage content view if the Storage tab was previously unvisited (r235242)
  • Fixed console.log() to show the passed string when a certain format is used (r235452)
  • Fixed the JSContext Inspector to correctly show Scripts in the Resources tab (r235226)

WebGL 2

  • Updated WebGL 2 implementation to handle READ_FRAMEBUFFER and default framebuffer specification conformance (r235417)

Web Assembly

  • Updated Web Assembly to parse wasm modules in a streaming fashion (r235420)

Safari extensions

  • Messages from a Safari App Extension to its content script are now delivered to the correct page after a back or forward navigation

September 10, 2018 08:00 PM

August 29, 2018

Release Notes for Safari Technology Preview 64

Surfin’ Safari

Safari Technology Preview Release 64 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 234684-235171.

Custom Elements

  • Fixed the custom element constructor to use HTMLElement in‘s realm (r234957)
  • Fixed custom element to invalidate its style when :defined rule starts to apply (r234953)
  • Changed invoking custom element reactions after constructing and inserting a custom element (r234893)
  • Changed to perform a microtask checkpoint before creating a custom element (r234944)


  • Added the content-length header to the Fetch safe-list (r234840)
  • Disallowed navigations when page cache updates the current document of the frame (r235121)
  • Fixed navigator.sendBeacon to work in pagehide callbacks (r234684)
  • Fixed <object> elements that change from hidden to visible to properly display its content if its URL has a fragment identifier (r234762)


  • Added Experimental Feature support for SourceBuffer.changeType() (r234940)
  • Fixed an issue causing video playback to use more power (r234743)
  • Skipped validation of ideal constraints when selecting matching getUserMedia devices (r234949)


  • Added support for a “name” option for dedicated workers (r235159)
  • Added support for unhandled promise rejections in a Worker (r234846)
  • Changed Date.UTC to not return NaN with only year parameter (r234763)
  • Changed Array.prototype.sort to throw a TypeError if the parameter is a not callable object (r234716)

Storage Access API

  • Changed to use eTLD+1s, not full host names, when granting storage access (r235145)

Web Inspector

  • Added support for breakpoints on arbitrary event names (r234974)
  • Added Initiator information in the Network table (r234963)
  • Allowed breakpoints to be set for specific event listeners (r235103)
  • Allowed recording processing to be stopped midway in the Canvas tab (r235095)
  • Created icons for recordings and shaders in the preview tile of the Canvas tab (r235093)
  • Fixed console.log to prevent firing getters for deep properties (r234780)
  • Fixed the contrast of the error and warning text widget for the source code text editor in Dark Mode (r234736)
  • Fixed XHR content sometimes showing as an error even though the load succeeded (r234702)
  • Fixed ⌘G to work as expected when the find banner is focused (r235147)
  • Provided a default icon for all actions in the Canvas tab (r235141)
  • Prevented tables from centering rows when scrolling them into view (r234882)


  • Changed top not handle prompts that appear while running scripts (r234792)
  • Included all capabilities in the new session response (r234837)
  • Stopped trying to set the caret when focusing a non-text element in the send keys command (r234838)


  • Implemented flow-relative margin, padding, border and sizing properties (r234798)
  • Updated the behavior of percentage row tracks and gutters in CSS Grid (r234687))


  • Fixed WebGL contexts to be updated when the display configuration is changed (r235125)

Bug Fix

  • Fixed color wells to appear pressed when presenting a color picker (r234788)

Safari Push Notifications

  • A user gesture, such as a mouse click, is now required to request the user’s permission to send Safari Push Notifications

Safari Reader

August 29, 2018 05:00 PM

August 15, 2018

Release Notes for Safari Technology Preview 63

Surfin’ Safari

Safari Technology Preview Release 63 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 234197-234684.

Known Issue

  • Adobe Flash content does not load on macOS Mojave

Dark Mode

  • Fixed the appearance of the Smart Search Field in Dark mode on macOS Mojave


  • Fixed a Safari Technology Preview application crash that could happen when waking one’s Mac from sleep (r234674)
  • Fixed a Safari Technology Preview application crash that could happen when navigating between web pages (234462)

Custom Elements

  • Fixed and document.write to throw errors while the HTML parser is synchronously constructing a custom element (r234680)
  • Implemented customElements.upgrade() (r234507)
  • Fixed erroneous garbage collection for properties set on window.customElements (r234578, r234585)
  • Changed innerHTML to not synchronously create a custom element (r234577)
  • Made HTML parser immediately execute custom elements reactions after synchronously constructing a custom element (r234608)
  • Fixed the crash that occurs when a custom element reaction callback throws an exception (r234539)


  • Prevented creating composited layers for renderers unless they are part of the fullscreen subtree (r234291)
  • Fixed switching tabs to not close the picture-in-picture window (r234264)

Web Animations

  • Fixed accelerated animations to respect a positive delay value (r234279)
  • Fixed transitions added immediately after element creation to work as expected (r234250)
  • Fixed animation stopping with object-fit:contain on an animated 2D canvas (r234343)


  • Fixed navigator.sendBeacon to work in pagehide event callbacks (r234684)
  • Fixed setting the table layout to fixed causing incorrect cell width calculations (r234630)


  • Fixed returning nothing for various previous text marker APIs from one <div> or <p> node to another (r234275)

Web Inspector

  • Fixed inconsistent background color for the JavaScript Debugger breakpoint editor in Dark Mode (r234219)
  • Fixed the contrast for the disabled breakpoints banner in Dark Mode (r234464)
  • Fixed a white background for the Search sidebar panel text field in Dark Mode (r234394)
  • Fixed the source code text editor thread indicator widget contrast in Dark Mode (r234465)
  • Included a full URL tooltip when hovering the name in the Network Tab (r234431)

Internationalization API

  • Changed the Internationalization API to ignore encoding when parsing BCP 47 language tag from an ISO 15897 locale string passed via LANG (r234260)

WebGL 2

  • Added support for compilation of GLSL ES version 300 shaders (r234380)


  • Changed to allow href attribute without xlink on SVG elements (r234683)

August 15, 2018 05:00 PM

August 09, 2018

Manuel Rego: Changes on CSS Grid Layout in percentages and indefinite height

Igalia WebKit

This is a blog post about a change of behavior on CSS Grid Layout related to percentage row tracks and gutters in grid containers with indefinite height. Igalia has just implemented the change in Chromium and WebKit, which can affect some websites out there. So here I am going to explain several things about how percentages work in CSS and all the issues around it, of course I will also explain the change we are doing in Grid Layout and how to keep your previous behavior in the new version with very simple changes.

Sorry for the length but I have been dealing with these issues since 2015 (probably earlier but that is the date of the first commit I found about this topic), and I went too deep explaining the concepts. Probably the post has some mistakes, this topic is not simple at all, but it represents a kind of brain dump of my knowledge about it.

Percentages and definite sizes

This is the easy part, if you have an element with fixed width and height resolving percentages on children dimensions is really simple, they are just computed against the width or height of the containing block.

A simple example:

<div style="width: 500px; height: 200px; border: dashed thick black;">
  <div style="width: 50%; height: 75%; background: magenta;"></div>

Example of percentage dimensions in a containing block with definite sizes Example of percentage dimensions in a containing block with definite sizes

Things are a bit trickier for percentage margins and paddings. In inline direction (width in horizontal writing mode) they work as expected and are resolved against the inline size. However in block direction (height) they are not resolved against the block size (as one can initially expect) but against the inline size (width) of the containing block.

Again a very simple example:

<div style="width: 500px; height: 200px; border: dashed thick black;">
  <div style="margin-left: 10%; margin-top: 10%;
              height: 150px; background: magenta;"></div>

Example of percentage margins in a containing block with definite sizes Example of percentage margins in a containing block with definite sizes

Note that there is something more here, in both Flexbox and Grid Layout specifications it was stated in the past that percentage margins and paddings resolve against their corresponding dimension, for example inline margins against inline axis and block margins against block axis.

This was implemented like that in Firefox and Edge, but Chromium and WebKit kept the usual behavior of resolving always against inline size. So for a while the spec had the possibility to resolve them in either way.

This was a source of interoperability issues between the different browsers but finally the CSS Working Group (CSSWG) resolved to keep the behavior for regular blocks also for flex and grid items. And both Firefox and Edge modified their behavior and all browsers have the same output nowadays.

Percentages and indefinite sizes

First question is, what is an indefinite size? The simple answer is that a definite size is a size that you can calculate without taking into account the contents of the element. An indefinite size is the opposite, in order to compute it you need to check the contents first.

But then, what happens when the containing block dimensions are indefinite? For example, a floated element has indefinite width (unless otherwise manually specified), a regular block has indefinite height by default (height: auto).

For heights this is very simple, percentages are directly ignored so they have no effect on the element, they are treated as auto.

For widths it starts to get funny. Web rendering engines have two phases to compute the width of an element. A first one to compute the minimum and maximum intrinsic width (basically the minimum and maximum width of its contents), and a second one to compute the final width for that box.

So let’s use an example to explain this properly. Before getting into that, let me tell you that I am going to use Ahem font in some examples, as it makes very easy to know the size of the text and resolve the percentages accordingly, so if we use font: 50px/1 Ahem; we know that the size of an X character is a square of 50x50 pixels.

<div style="float: left; font: 50px/1 Ahem;
            border: solid thick black; background: magenta; color: cyan;">

Example of intrisic width without constraints Example of intrisic width without constraints

The browser first calculates the intrinsic width, as minimum it computes 250px (the size of the smallest word, XXXXX in this case), as maximum size it would be 400px (the size of the whole text without line breaking XX XXXXX). So after this phase the browser knows that the element should have a width between 250px and 400px.

Then during layout phase the browser will decide the final size, if there are no constraints imposed by the containing block it will use the maximum intrinsic width (400px in this case). But if you have a wrapper with a 300px width, the element will have to use 300px as width. If you have a wrapper smaller than the minimium intrinsic width, for example 100px, the element will still use the minimum 250px as its size. This is a quick and dirty explanation, but I hope it is useful to get the general idea.

Example of intrisic width width different constraints Example of intrisic width with different constraints

In order to resolve percentage widths (in the indefinite width situations) the browser does a different thing depending on the phase. During intrinsic size computations the percentage width is ignored (treated as auto like for the heights). But in the layout phase the width is resolved against the intrinsic size computed earlier.

Trying to summarize the above paragraphs, we can say that somehow the width is only indefinite while the browser is computing the intrinsic width of the element, afterwards during the actual layout the width is considered definite and percentages are resolved against it.

So now let’s see an example of indefinite dimensions and percentages:

<div style="float: left;
            border: solid thick black; background: magenta;">
  <div style="width: 50%; height: 50%; background: cyan;">Hello world!</div>

Example of percentage dimensions in a containing block with indefinite sizes Example of percentage dimensions in a containing block with indefinite sizes

First the size of the magenta box is calculated based on its contents, as it has not any constraint it uses the maximum intrinsic width (the length of Hello world!). Then as you can see the width of the cyan box is 50% of the text length, but the height is the same than if we use height: auto (the default value), so the 50% height is ignored.

Back-compute percentages

For margins and paddings things work more or less the same, remember that all of them are resolved against the inline direction (so they are ignored during intrinsic size computation and resolved later during layout).

But there is something special about this too. Nowadays all the browsers have the same behavior but that was not always the case, not so long time ago (before Firefox 61 which was released past June) things worked different in Firefox than the rest of browsers

Again let’s go to an example:

<div style="float: left; font: 50px/1 Ahem;
            border: solid thick black; background: magenta;">
  <div style="margin-left: 50%; height: 100px;
              background: cyan; color: blue;">XXXXX</div>

Example of percentage margins in a containing block with indefinite sizes Example of percentage margins in a containing block with indefinite sizes

In this example the size of the magenta box (the floated div) is the width of the text, 250px in this case. Then the margin is 50% of that size (125px), making that the size of the cyan box gets reduced to 125px too, which causes overflow.

But for these cases (percentage width margins and paddings and indefinite width container) Firefox did something extra that was called back-compute percentages. For that it something similar to the following formula:

Intrinsic width / (1 - Sum of percentages)

Which for this case would be 250px / (1 - 0.50) = 500px. So it takes as intrinsic size of the magenta box 500px, and then it resolves the 50% margin against it (250px). Thanks to this there is no overflow, and the margin is 50% of the containing block size.

Example of old Firefox behavior back-computing percentage margins Example of old Firefox behavior back-computing percentage margins

This Firefox behavior seems really smart and avoid overflows, but the CSSWG discussed about it and decided to use the other behavior. The main reason is what happens when you are around 100% percentages, or if you go over that value. The size of the box starts to be quite big (with 90% margin it would be 2500px), and when you go to 100% or over it you cannot use that formula so it considers the size as infinity (basically the viewport size in this example) and there is discontinuity in how percentages are resolved.

So after that resolution Firefox changed their implementation and removed the back-computing percentages logic, thus we have now interoperability in how percentage margins and paddings are resolved.

CSS Grid Layout and percentages

And now we arrive to CSS Grid Layout and how to resolve percentages in two places: grid tracks and grid gutters.

Of course when the grid container has definite dimensions there are no problems in resolving percentages against them, that is pretty simple.

As usual the problem starts with indefinite sizes. Originally this was not a controversial topic, percentages for tracks were behaving similar to percentage for dimensions in regular blocks. A percentage column was treated as auto for intrinsic size computation and later resolved against that size during layout. For percentage rows they were treated as auto. It does not mean that this is very easy to understand (actually it took me a while), but once you get it, it is fine and not hard to implement.

But when percentage support was added to grid gutters the big party started. Firefox was the first browser implementing them and they decided to use the back-compute technique explained in the previous point. Then when we add support in Chromium and WebKit we did something different than Firefox, we basically mimic the behavior of percentage tracks. As browsers started to diverge different discussions appear.

One of the first agreements on the topic was that both percentage tracks and gutters should behave the same. That invalidated the back-computing approach, as it was not going to work fine for percentage tracks as they have contents. In addition it was finally discarded even for regular blocks, as commented earlier, so this was out of the discussion.

However the debate moved to how percentage row tracks and gutters should be resolved, if similar to what we do for regular blocks or if similar to what we do for columns. The CSSWG decided they would like to keep CSS Grid Layout as symmetric as possible, so making row percentages resolve against the intrinsic height would achieve that goal

So finally the CSSWG resolved to modify how percentage row tracks and gutters are resolved for grid containers with indefinite height. The two GitHub issues with the last discussions are: #509 and #1921.

Let’s finish this point with a pair of examples to understand the change better comparing the previous and new behavior.

Percentage tracks:

<div style="display: inline-grid; border: solid thick;
            grid-template-columns: 75%; grid-template-rows: 50%;">
  <div style="background: magenta;">Testing</div>

Example of percentage tracks in a grid container with indefinite sizes Example of percentage tracks in a grid container with indefinite sizes

Here the intrinsic size of the grid container is the width and height of the text Testing, and then the percentages tracks are resolved against that size for both columns and rows (before that was only done for columns).

Percentage gutters:

<div style="display: inline-grid; grid-gap: 10%; border: solid thick;
            grid-template-columns: 200px 200px; grid-template-rows: 100px 100px;">
  <div style="background: magenta;"></div>
  <div style="background: cyan;"></div>
  <div style="background: yellow;"></div>
  <div style="background: lime;"></div>

Example of percentage gutters in a grid container with indefinite sizes Example of percentage gutters in a grid container with indefinite sizes

In this example we can see the same thing, with the new behavior both the percentage column and row gaps are resolved against the intrinsic size.

Change behavior for indefinite height grid containers

For a while all browsers were behaving the same (after Firefox dropped the back-computing approach) so changing this behavior would imply some kind of risks, as some websites might be affected by that and get broken.

For that reason we added a use counter to track how many websites where hitting this situation, using percentage row tracks in a indefinite height grid container. The number is not very high, but there is an increasing trend as Grid Layout is being adopted (almost 1% of websites are using it today).

And then Firefox changed the behavior for percentage row gutters to follow the new text on the spec, so they are resolved against the intrinsic height (this happened in version 62). However it did not change the behavior for percentage row tracks yet.

This was a trigger to retake the topic and go deeper on it, after analyzing it carefully and crafting a prototype implementation we sent an intent to implement and ship to blink-dev mailing list.

The intent was approved, but we were requested to analyze the sites that were hitting the use counter. After checking 178 websites only 8 got broken due to this change, we contacted them to try to get them fixed explaining how to keep the previous behavior (more about this in next point). You can find more details about this research in this mail.

Apart from that we added a deprecation message in Chromium 69, so if you have a website that is affected by this (it does not mean that it has to get broken but that it uses percentage row tracks in a grid container with indefinite height) you will get the following warning in the JavaScript console:

[Deprecation] Percentages row tracks and gutters for indefinite height grid containers will be resolved against the intrinsic height instead of being treated as auto and zero respectively. This change will happen in M70, around October 2018. See for more details.

Finally this week the patch has been accepted and merged in master, so since Chromium 70.0.3516 (current Canary) you will have the new behavior. Apart from that we also make the fix in WebKit that will be hopefully part of the next Safari releases.

In addition Firefox and Edge developers have been notified and we have shared the tests in WPT as usual, so hopefully those implementations will get updated soon too.

Update your website

Yes this change might affect your website or not, even if you get the deprecation warning it can be the case that your website is still working perfectly fine, but in some cases it can break quite badly. The good news is that the solution is really straightforward.

If you find issues in your website and you want to keep the old behavior you just need to do the following for grid containers with indefinite height:

  • Change percentages in grid-template-rows or grid-auto-rows to auto.
  • Modify percentages in row-gap or grid-row-gap to 0.

With those changes your website will keep behaving like before. In most cases you will realize that the percentages were unneeded and were not doing anything useful for you, even you would be able to drop the declaration completely.

One of these cases would be websites that have grid containers with just one single row of 100% height (grid-template-rows: 100%), many of the sites hitting the use counter are like this. All these are not affected by this change, unless the have extra implicit rows, but the 100% is not really useful at all there, they can simply remove the declaration.

Another sites that have issues are the ones that have for example two rows that sum up 100% in total (grid-template-rows: 25% 75%). These percentages were ignored before, so the contents always fit in each of the rows. Now the contents might not fit in each row and the results might not be the desired ones. Example:

<div style="display: grid; grid-template-rows: 25% 75%; border: solid thick;">
  <div style="background: magenta;">First<br>two lines</div>
  <div style="background: cyan;">Second</div>

Example of overlapping rows in the new behavior Example of overlapping rows in the new behavior

The sites that were more broken usually have several rows and used percentages only for a few of them or for all. And now the rows overflow the height of the grid container and they overlap other content on the website. There were cases like this example:

<div style="display: grid; grid-template-rows: 50%; border: solid thick;">
  <div style="background: magenta;">First</div>
  <div style="background: cyan; height: 200px;">Second</div>
  <div style="background: yellow; height: 100px;">Third</div>

Example of overflowing rows in the new behavior Example of overflowing rows in the new behavior


This topic has been a kind of neverending story for the CSSWG, but finally it seems we are reaching to an end. Let’s hope this does not get any further and things get settle down after all this time. We hope that this change is the best solution for web authors and everyone will be happy with the final outcome.

As usual I could not forget to highlight that all this work has been done by Igalia thanks to Bloomberg sponsorship as part of our ongoing collaboration.

Igalia and Bloomberg working together to build a better web Igalia and Bloomberg working together to build a better web

Thanks for reading that long, this ended up being much more verbose and covering more topics than originally planned. But I hope it can be useful to understand the whole thing. You can find all the examples from this blog post in this pen feel free to play with them.

And to finish this blog post I could only do it by quoting fantasai:

this is why I hate percentages in CSS

I cannot agree more with her. 😇

August 09, 2018 10:00 PM

August 07, 2018

Manuel Rego: CSS Logical Properties and Values in Chromium and WebKit

Igalia WebKit

Since the beginning of the web we have been used to deal with physical CSS properties for different features, for example we all know how to set a margin in an element using margin-left, margin-right, margin-top and/or margin-bottom. But with the appearance of CSS Writing Modes features, the concepts of left, right, top and bottom have somehow lost their meaning.

Imagine that you have some right-to-left (RTL) content on your website your left might be probably the physical right, so if you are usually setting margin-left: 100px for some elements, you might want to replace that with margin-right: 100px. But what happens if you have mixed content left-to-right (LTR) and RTL at the same time, then you will need different CSS properties to set left or right depending on that. Similar issues are present if you think about vertical writing modes, maybe left for that content is the physical top or bottom.

CSS Logical Properties and Values is a CSS specification that defines a set of logical (instead of physical) properties and values to prevent this kind of issues. So when you want to set that margin-left: 100px independently of the direction and writing mode of your content, you can directly use margin-inline-start: 100px that will be smart enough. Rachel Andrew has a nice blog post explaining deeply this specification and its relevance.

Example of 'margin-inline-start: 100px' in different combinations of directions and writing modes Example of margin-inline-start: 100px in different combinations of directions and writing modes

Oriol Brufau, an active collaborator on the CSS Working Group (CSSWG), has been doing a Igalia Coding Experience implementing support for CSS Logical Properties and Values in Blink and WebKit. Maybe you were already aware of this as my colleague Frédéric Wang already talked about it in his last blog post reviewing the activities of Igalia Web Platform team in the past semester.

Some history

Chromium and WebKit have had support since a long time ago for some of the CSS logical properties defined by the spec. But they were not using the standard names defined in the specification but some -webkit- prefixed ones with different names.

For setting the dimensions of an element Chromium and WebKit have properties like -webkit-logical-width and -webkit-logical-height. However CSS Logical defines inline-size and block-size instead. There are also the equivalent ones for minimum and maximum sizes too. These ones have been already unprefixed at the beginning of 2017 and included in Chromium since version 57 (March 2017). In WebKit they are still only supported using the prefixed version.

But there are more similar properties for margins, paddings and borders in Chromium and WebKit that use start and end for inline direction and before and after for block direction. In CSS Logical we have inline-start and inline-end for inline direction and block-start and block-end for block direction, which are much less confusing. There was an attempt in the past to unprefix these properties but the work was abandoned and never completed. These ones were still using the -webkit- prefix so we decided to tackle them as the first task.

The post has been only talking about properties so far, but the same thing applies to some CSS values, that is why the spec is called CSS Logical Properties and Values. For example a very well-known property like float has the physical values left and right. The spec defines inline-start and inline-end as the logical values for float. However these were not supported yet in Chromium and WebKit, not even using -webkit- prefixes.

Firefox used to have some -moz- prefixed properties, but since Firefox 41 (September 2015) it is shipping many of the standard logical properties and values. Firefox has been using these properties extensively in its own tests, thus having them supported in Chromium will make easier to share them.

At the beginning of this work, Oriol wrote a document in which explaining the implementation plan where you can check the status of all these properties in Chromium and Firefox.

Unprefix existent properties

We originally send an intent to implement and ship for the whole spec, actually not all the spec but the parts that the CSSWG considered ready to implement. But Chromium community decided it was better to split it in two parts:

The work on the first part, making the old -webkit- prefixed properties to use the new standard names, has been already completed by Oriol and it is going to be included in the upcoming release of Chromium 69.

In addition to the Chromium work Oriol has just started to do this on WebKit too. Work is on early stages here but hopefully things will move forward in parallel to the Chromium stuff.

Adding support for the rest

Next step was to add support for the new stuff behind an experimental flag. This work is ongoing and you can check the current status in the latest Canary enabling the Experimental Web Platform features flag.

So far Oriol has added support for a bunch of shorthands and the flow-relative offset properties. You can follow the work in issue #850004 in Chromium bug tracker.

We will talk more about this in a future blog post once this task is completed and the new logical properties and values are shipped.


Of course testing is a key part of all these tasks, and web-platform-tests (WPT) repository plays a fundamental role to ensure interoperability between the different implementations. Like we have been doing in Igalia lately in all our developments we used WPT as the primary place to store all the tests related to this work.

Oriol has been creating tests in WPT to cover all these features. Initial tests were based in the ones already available in Firefox and modified them to adapt to the rest of stuff that needs to be checked.

Note that in Chromium all the sideways writing modes test cases are failing as there is no support for sideways in Chromium yet.

Plans for the future

As explained before, this is an ongoing task but we already have some extra plans for it. These are some of the tasks (in no particular order) that we would like to do in the coming months:

  • Complete the implementation of CSS Logical Properties and Values in Chromium. This was explained in the previous point and is moving forward at a good pace.
  • Get rid of usage of -webkit- prefixed properties in Chromium source code. Oriol has also started this task and is currently work in progress.
  • Deprecate and remove the -webkit- prefixed properties. It still too early for that but we will keep an eye on the metrics and do it once usage has decreased.
  • Implement it in WebKit too, first by unprefixing the current properties (which has been already started) and later continuing with the new things. It would be really nice if WebKit follows Chromium on this. Edge also has plans to add support for this spec, so that would make logical properties and values available in all the major browsers.

Wrap up

Oriol has been doing a good job here as part of his Igalia Coding Experience. Apart from all the new stuff that is landing in Chromium, he has also been fixing some related bugs.

We have just started the WebKit tasks, but we hope all this work can be part of future Chromium and Safari releases in the short term.

And that is all for now, we will keep you posted! 😉

August 07, 2018 10:00 PM

August 05, 2018

ITP Debug Mode in Safari Technology Preview 62

Surfin’ Safari

One of the more frequent questions we get from developers regarding Safari’s Intelligent Tracking Prevention (ITP) is how to debug your website with it enabled, especially since it is enabled by default in Safari. Today we’re happy to present you with an experimental version of ITP Debug Mode. Please try it out and send us feedback.

Enable ITP Debug Mode

This is how you enable ITP Debug Mode in Safari Technology Preview 62:

  1. Click the Safari Technology Preview menu → Preferences → Advanced
  2. Enable the Develop menu by clicking the checkbox next to “Show Develop menu in the menu bar”
  3. Click the Develop menu → Experimental Features → ITP Debug Mode

Disable ITP Debug Mode After Use

ITP Debug Mode should only be used when actively debugging your website for Intelligent Tracking Prevention behaviors. Remember to disable ITP Debug Mode when you’re done debugging. Why?

For privacy reasons, ITP Debug Mode logs on the INFO level to ensure domain names are not written to persistent log files. If you leave ITP Debug Mode enabled, you run the risk of having privacy-sensitive domain names included in your logs when running some system diagnostic tools, like capturing a sysdiagnose.

Domains Classified by Intelligent Tracking Prevention

When launching Safari Technology Preview, ITP Debug Mode logs which domains ITP has classified as having cross-site tracking abilities. To see these logs, do the following:

  1. Quit Safari Technology Preview
  2. Filter ITP Debug Mode log messages using the Console app or Terminal app
    1. If you prefer the Console app:
      1. Launch the Console app
      2. Click the Action menu → Include Info Messages
      3. Filter on “ResourceLoadStatisticsDebug” without the quotes
    2. If you prefer Terminal:
log stream -info | grep ResourceLoadStatisticsDebug
  1. Launch Safari Technology Preview

You will now see which domains ITP has already classified as having tracking abilities in one or more log statements, such as:

About to block cookies in third-party contexts for: is set up to always be classified as a tracker in ITP Debug Mode and you can use it to test functionality such as the Storage Access API.

Depending on how much browsing you’ve done since starting fresh (see the “Starting Fresh” section below), you’ll see anything from just to hundreds of domain names listed in these log statements.

Further Logging as You Browse the Web

OK, so you’ve enabled ITP Debug Mode, set up Console or Terminal to capture the right logs, launched Safari Technology Preview, and seen the initial ITP Debug Mode logs. From this point you will see new log statements whenever Intelligent Tracking Prevention makes a new decision.

Such as when it purges website data:

About to remove data records for tracker.example, another-tracker.example.

When it classifies a new domain as having tracking abilities:

About to block cookies in third-party contexts for: a-third-tracker.example.

Or, when it prompts the user as a result of a call to the Storage Access API:

About to ask the user whether they want to grant storage access to under news.example or not.

Classifying A Custom Domain For Testing

One specific request we received from developers was for the ability to manually set a custom domain as permanently classified with tracking abilities. With ITP Debug Mode and User Defaults, that is now possible. Open Terminal and execute the following command (in this example to set as permanently classified):

defaults write ResourceLoadStatisticsManualPrevalentResource

When you launch Safari Technology Preview with ITP Debug Mode enabled, you will now see this added log statement in Console or Terminal:

Did set as prevalent resource for the purposes of ITP Debug Mode.

You can inspect the setting in Terminal like this:

defaults read ResourceLoadStatisticsManualPrevalentResource

And you can delete the setting like this:

defaults delete ResourceLoadStatisticsManualPrevalentResource

Starting Fresh

When you’re debugging under Intelligent Tracking Prevention, it’s often useful to start fresh. You do that by deleting all Safari Technology Preview history. This not only deletes history and website data, but also resets ITP. Clearing your history will also sync with other devices over iCloud. To avoid that, we recommend creating a new user on your macOS system to use exclusively for debugging Intelligent Tracking Prevention. Be careful though. If you’re investigating an issue that is the result of real life browsing, resetting ITP may prevent you from reproducing the issue, since all of ITP’s data is deleted and the real life browsing that got you into the state with the issue may not be something you can replicate.

In ITP Debug Mode, and any custom domain you’ve set up through User Defaults stay classified even when you delete history. This behavior provides for controlled, repeatable testing.

Feedback and Bug Reports

Please report bugs about ITP Debug Mode using the WebKit bug tracker at, and send feedback to our evangelist Jon Davis. If you have technical questions on debugging with ITP Debug Mode you can find me on Twitter @johnwilander.

August 05, 2018 05:00 PM

August 01, 2018

Release Notes for Safari Technology Preview 62

Surfin’ Safari

Safari Technology Preview Release 62 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 233728-234197.

Known Issues

  • This release of Safari Technology Preview for macOS Mojave betas does not render text properly in the Smart Search Field when in Dark Mode.
  • This release of Safari Technology Preview for macOS Mojave betas does not have a usable WebDriver implementation; safaridriver hangs when processing the New Session command.

Intelligent Tracking Prevention

  • Added an experimental ITP Debug Mode to be used only when actively debugging, not to remain enabled (r234080, r234108)


  • Changed to canonical language tags in the Internationalization API (r234127)
  • Fixed the Generator and AsyncGeneratorMethod prototype (r233855)
  • Fixed the JSON.stringify replacer to use isArray instead of JSArray checks (r233918)
  • Fixed the iterator of Array.keys() to return the object in the correct order (r233740)
  • Fixed JavaScript URL to provide the correct result when frame is navigated (r233793)
  • Changed JSON.stringify to emit properties included in the prototype chain for entries in the second array argument (r233924)


  • Changed to require the document to be visible for fullscreen video (r233865)
  • Disabled all network caching for HLS streams. (r233738)
  • Fixed the transition for the first Picture-in-Picture from Fullscreen (r234051)
  • Changed HLS resources with remote sub-resources to taint media elements (r234055)
  • Improved WebGL selection of GPU driving the current display (r234074)


  • Fixed newly added float elements to trigger full layout on the block (r233767)

Dark Mode

  • Improved the visibility of spelling and grammar markers in Dark Mode (r233814)


  • Limited editing selections to within Shadow DOM boundaries (r233778)

Web Inspector


  • Implemented support for margin-box as reference box and box shape (r233886)
  • Added full support for -webkit-clip-path on SVG elements (r233835, r234136)

Web Animations

  • Changed to discrete interpolation between font-styles with a keyword value (r233935)
  • Changed to discrete interpolation between lengths with an auto value (r233892)


  • Added support for calc() in CSS Grid gutter properties (r234131)


  • Fixed the ability to remove the database file of a sub-frame (r233777)


  • Fixed pressing tab to highlight items on a webpage when voiceover enabled (r234112)

August 01, 2018 05:00 PM

July 21, 2018

Michael Catanzaro: On Flatpak Nightlies

Igalia WebKit

Here’s a little timeline of some fun we had with the GNOME master Flatpak runtime last week:

  • Tuesday, July 10: a bad runtime build is published.  Trying to start any application results in error while loading shared libraries: cannot open shared object file: No such file or directory. Problem is the library is present in org.gnome.Sdk instead of org.gnome.Platform, where it is required.
  • Thursday, July 12:  the bug is reported on WebKit Bugzilla (since it broke Epiphany Technology Preview)
  • Saturday, July 14: having returned from GUADEC, I notice the bug report and bisect the issue to a particular runtime build. Mathieu Bridon fixes the issue in the freedesktop SDK and opens a merge request.
  • Monday, July 16: Mathieu’s fix is committed. We now have to wait until Tuesday for the next build.
  • Tuesday, Wednesday, and Thursday: we deal with various runtime build failures. Each day, we get a new build log and try to fix whatever build failure is reported. Then, we wait until the next day and see what the next failure is. (I’m not aware of any way to build the runtime locally. No doubt it’s possible somehow, but there are no instructions for doing so.)
  • Friday, July 20: we wait. The build has succeeded and the log indicates the build has been published, but it’s not yet available via flatpak update
  • Saturday, July 21: the successful build is now available. The problem is fixed.

As far as I know, it was not possible to run any nightly applications during this two week period, except developer applications like Builder that depend on org.gnome.Sdk instead of the normal org.gnome.Platform. If you used Epiphany Technology Preview and wanted a functioning web browser, you had to run arcane commands to revert to the last good runtime version.

This multi-week response time is fairly typical for us. We need to improve our workflow somehow. It would be nice to be able to immediately revert to the last good build once a problem has been identified, for instance.

Meanwhile, even when the runtime is working fine, some apps have been broken for months without anyone noticing or caring. Perhaps it’s time for a rethink on how we handle nightly apps. It seems likely that only a few apps, like Builder and Epiphany, are actually being regularly used. The release team has some hazy future plans to take over responsibility for the nightly apps (but we have to take over the runtimes first, since those are more important), and we’ll need to somehow avoid these issues when we do so. Having some form of notifications for failed builds would be a good first step.

P.S. To avoid any possible misunderstandings: the client-side Flatpak technology itself is very good. It’s only the server-side infrastructure that is problematic here. Clearly we have a lot to fix, but it won’t require any changes in Flatpak.

By Michael Catanzaro at July 21, 2018 02:12 PM

July 18, 2018

Release Notes for Safari Technology Preview 61

Surfin’ Safari

Safari Technology Preview Release 61 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 233256-233728.


  • Fixed -webkit-clip-path offset for clipPath references (r233287)
  • Turned CSS Animation Triggers off by default (r233265)
  • Updated clip-path box mapping to unified box (r233302)

Dark Mode

  • Made the focus ring color honor the system accent color (r233315)
  • Prevented inverting text color for selections when not in dark mode (r233532)


  • Enabled Link Preload by default in the Experimental Features menu (r233263)
  • Fixed cookie creation time exposed to Objective-C (r233308)
  • Fixed find in page to find low (German) quotes (r233345)
  • Fixed return values for DOMMatrix.invertSelf() when used on a non-invertible matrix (r233628)
  • Implemented support for Element.toggleAttribute (r233475)
  • Improved window.event compliance: Should not be set when target is in shadow tree (r233489)
  • Promoted the Secure Context API from an experimental feature to always on (r233264)
  • Updated the Element API to use qualifiedName to comply with standards (r233545)

Service Workers

  • Made fetch() use “same-origin” credentials by default (r233720)
  • Fixed fetching several times in a row (r233719)


  • Disabled autoplay when the element is suspended (r233485)
  • Fixed video flicker which sometimes happened when playing to AppleTV (r233435, r233535)
  • Changed to reject getUserMedia promise if capture fails (r233425)


  • Fixed delay and video lag caused by enabling and disabling a MediStreamTrack (r233604)

Web Assembly

  • Stopped using tracePoints in JavaScript/WASM entry (r233378)

Web Inspector

  • Fixed copy from Search results content view (r233334)
  • Fixed the “Open Link” context menu action (r233316)
  • Fixed the resource search field in dark mode (r233608)
  • Fixed the Debugger content view to properly update when the left sidebar is collapsed (r233686)
  • Enabled control-dragging to pan the 3D render in the Layers inspector (r233695)


  • Added a subrole for meter elements on macOS (r233607)
  • Fixed setValue on text controls to send out key events (r233525, r233580)

July 18, 2018 05:20 PM

July 09, 2018

Frédéric Wang: Review of Igalia's Web Platform activities (H1 2018)

Igalia WebKit

This is the semiyearly report to let people know a bit more about Igalia’s activities around the Web Platform, focusing on the activity of the first semester of year 2018.



Igalia has proposed and developed the specification for BigInt, enabling math on arbitrary-sized integers in JavaScript. Igalia has been developing implementations in SpiderMonkey and JSC, where core patches have landed. Chrome and Node.js shipped implementations of BigInt, and the proposal is at Stage 3 in TC39.

Igalia is also continuing to develop several features for JavaScript classes, including class fields. We developed a prototype implementation of class fields in JSC. We have maintained Stage 3 in TC39 for our specification of class features, including static variants.

We also participated to WebAssembly (now at First Public Working Draft) and internationalization features for new features such as Intl.RelativeTimeFormat (currently at Stage 3).

Finally, we have written more tests for JS language features, performed maintenance and optimization and participated to other spec discussions at TC39. Among performance optimizations, we have contributed a significant optimization to Promise performance to V8.


Igalia has continued the standardization effort at the W3C. We are pleased to announce that the following milestones have been reached:

A new charter for the ARIA WG as well as drafts for ARIA 1.2 and Core Accessibility API Mappings 1.2 are in preparation and are expected to be published this summer.

On the development side, we implemented new ARIA features and fixed several bugs in WebKit and Gecko. We have refined platform-specific tools that are needed to automate accessibility Web Platform Tests (examine the accessibility tree, obtain information about accessible objects, listen for accessibility events, etc) and hope we will be able to integrate them in Web Platform Tests. Finally we continued maintenance of the Orca screen reader, in particular fixing some accessibility-event-flood issues in Caja and Nautilus that had significant impact on Orca users.

Web Platform Predictability

Thanks to support from Bloomberg, we were able to improve interoperability for various Editing/Selection use cases. For example when using backspace to delete text content just after a table (W3C issue) or deleting a list item inside a content cell.

We were also pleased to continue our collaboration with the AMP project. They provide us a list of bugs and enhancement requests (mostly for the WebKit iOS port) with concrete use cases and repro cases. We check the status and plans in WebKit, do debugging/analysis and of course actually submit patches to address the issues. That’s not always easy (e.g. when it is touching proprietary code or requires to find some specific reviewers) but at least we make discussions move forward. The topics are very diverse, it can be about MessageChannel API, CSSOM View, CSS transitions, CSS animations, iOS frame scrolling custom elements or navigating special links and many others.

In general, our projects are always a good opportunity to write new Web Platform Tests import them in WebKit/Chromium/Mozilla or improve the testing infrastructure. We have been able to work on tests for several specifications we work on.


Thanks to support from Bloomberg we’ve been pursuing our activities around CSS:

We also got more involved in the CSS Working Group, in particular participating to the face-to-face meeting in Berlin and will attend TPAC’s meeting in October.


We have also continued improving the web platform implementation of some Linux ports of WebKit (namely GTK and WPE). A lot of this work was possible thanks to the financial support of Metrological.

Other activities

Preparation of Web Engines Hackfest 2018

Igalia has been organizing and hosting the Web Engines Hackfest since 2009, a three days event where Web Platform developers can meet, discuss and work together. We are still working on the list of invited, sponsors and talks but you can already save the date: It will happen from 1st to 3rd of October in A Coruña!

New Igalians

This semester, new developers have joined Igalia to pursue the Web platform effort:

  • Rob Buis, a Dutch developer currently living in Germany. He is a well-known member of the Chromium community and is currently helping on the web platform implementation in WebKit.

  • Qiuyi Zhang (Joyee), based in China is a prominent member of the Node.js community who is now also assisting our compilers team on V8 developments.

  • Dominik Infuer, an Austrian specialist in compilers and programming language implementation who is currently helping on our JSC effort.

Coding Experience Programs

Two students have started a coding experience program some weeks ago:

  • Oriol Brufau, a recent graduate in math from Spain who has been an active collaborator of the CSS Working Group and a contributor to the Mozilla project. He is working on the CSS Logical Properties and Values specification, implementing it in Chromium implementation.

  • Darshan Kadu, a computer science student from India, who contributed to GIMP and Blender. He is working on Web Platform Tests with focus on WebKit’s infrastructure and the GTK & WPE ports in particular.

Additionally, Caio Lima is continuing his coding experience in Igalia and is among other things working on implementing BigInt in JSC.


Thank you for reading this blog post and we look forward to more work on the web platform this semester!

July 09, 2018 10:00 PM

July 03, 2018

Release Notes for Safari Technology Preview 60

Surfin’ Safari

Safari Technology Preview Release 60 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 232790-233256.

Known Issues

  • Safari Technology Preview Release 60 will crash on launch on macOS Mojave Developer Beta 1. Users should upgrade to macOS Mojave Developer Beta 2 to avoid the crash.
  • After updating to Safari Technology Preview Release 60, the homepage preference and the Develop menu preference will be lost.

Web Animations

  • Changed CSS Animations to take precedence over CSS Transitions (r232868)
  • Ensured animations are updated prior to requestAnimationFrame callbacks (r233140)
  • Implemented the starting of CSS Transitions according to the standards specifications (r232946)

Dark Mode

  • Fixed input form controls with a white background in dark mode (r232806)
  • Fixed the white corner between vertical and horizon scrollbars in dark mode (r233116)

Web Inspector

  • Fixed all non-Same-Site cookies getting marked as Same-Site Strict in the Storage tab (r233027)
  • Fixed the Box Model section to have dark background in dark mode (r233187)
  • Fixed color outline that was too dark in dark mode (r233156)
  • Fixed font guideline colors that were too bright in dark mode (r233152)
  • Fixed media query names that were unreadable in dark mode (r233154)
  • Fixed network headers colors are too dim in dark mode (r233153)


  • Fixed the AirPlay picker to use the correct theme in dark mode (r233214)


  • Fixed CSS background-color style to no longer affect natively rendered text fields (r232799)
  • Exposed more semantic system colors (r232847)


  • Changed RTCRtpSender.replaceTrack(null) to stop the real-time source but keep the track (r232956)


  • Changed CSP to apply checks before content blocker checks for network loads to match cache load behavior (r232849)
  • Validated Cross-Origin-Resource-Policy for resources cached in the MemoryCache (r232933)


  • Fixed plug-in process crashing that affected Flash on macOS Mojave betas (r232848)

Intelligent Tracking Prevention

  • Improved classification of redirect collusion to a prevalent resource (r232850)


  • Fixed key actions to support multiple pressed virtual keys (r233131)
  • Included correct key code with synthesized NSEvents used for keystrokes (r233149)


  • Fixed focus to follow the text cursor when zoom is enabled (r232944)

July 03, 2018 05:00 PM

June 20, 2018

Web Animations in WebKit

Surfin’ Safari

Over the last 8 months we have been working on adding support for Web Animations, a W3C standard offering Web developers a JavaScript API to create, query and controls animations. While there is work left to do to ship this experimental feature to the Web at large, we feel our implementation has matured enough that, with the release of Safari Technology Preview 59, we can turn Web Animations on by default for our Web developer audience.

An Animation API for the Web

Browser engines have supported various animation features for many years, CSS Transitions and CSS Animations being two widely-supported approaches to authoring efficient animations on the Web. While these features have proven popular, they become limited when developers try to integrate browser-implemented animations via JavaScript:

  • Creating a CSS Transition dynamically requires forcing or waiting for a style invalidation so start and end values can be specified
  • Creating CSS Animations dynamically requires @keyframe rules to be generated and inserted in a global stylesheet
  • Animations created via CSS are not represented via JavaScript and cannot be queried or controlled

For instance, developers would have to resort to code such as this to slide an element 100 pixels to the right:

const element = document.getElementById("my-element");

// Set the start value and transition properties. = "translateX(0)"; = "transform"; = "1s";

// Force a style invalidation.

// Set the end value. = "translateX(100px)";

This approach is not elegant as it forces a style invalidation that causes extra work rather than just letting the browser invalidate styles at the most appropriate time. And this is just one single transition, but what if another library in your webpage also needed to create a transition? This would multiply forced style invalidation for no good reason.

The value of Web Animations lies in having a JavaScript API that preserves the ability to let the browser engine do the heavy lifting of running animations efficiently while enabling more advanced control of your animations. Using Web Animations, we can rewrite the code above with a single method call:¬…

element.animate({ transform: ["translateX(0)", "translateX(100px)"] }, 1000);

A single method call and you’re done! But that’s not all, now you can harness the power of Web Animations with a full-featured API to control this animation:

// Obtain a reference to the animation we created above.
const animation = element.getAnimations()[0];
// Seek the animation to 500ms.
animation.currentTime = 500;
// Pause the animation.

The Web Animations API is very powerful, for instance letting you get a list of all running animations on the document or an individual element, use promises to run code when an animation is ready to start or has completed, reverse an animation, etc.

Integration with CSS

The Web Animations specification goes further than specifying a JavaScript API. It provides a timing and animation model for web browsers to implement features such as CSS Transitions and CSS Animations. In fact, in WebKit, we’ve updated our implementation of these existing CSS technologies so that the same CSS Transitions and Animations you’ve been authoring for years are now represented as Web Animations objects in the browser. Using the getAnimations() method, you can obtain a reference to a CSSTransition or CSSAnimation object which are Animation subclasses. Then you can seek or pause a CSS transition running on an element just like we did above with an animation created using element.animate(). As a developer, you can think of CSS Transitions and Animations as a declarative layer above Web Animations.

Help Wanted

We’re very excited to be bringing the power of Web Animations to WebKit and enabling the technology in Safari Technology Preview 59. But there is still a fair bit of work ahead and we need your help to ensure we have a quality implementation before enabling the feature in Safari. We encourage you to try the new API and report issues that you find, bearing in mind that our current implementation is a bit behind the current state of the specification, and you can track all API changes with bug #186518.

It’s also important to check your existing content using CSS Transitions and Animations for possible regressions. One way to see if a regression you might be seeing is caused by the new Web Animations implementation, try toggling “Web Animations and CSS Integration” under the DevelopExperimental Features menu and see if your page’s behavior differs.

June 20, 2018 05:00 PM

Release Notes for Safari Technology Preview 59

Surfin’ Safari

Safari Technology Preview Release 59 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 232108-232790.

Known Issues

  • This release of Safari Technology Preview for macOS Mojave betas does not render text properly in the Smart Search Field when in Dark Mode
  • Users running this version of Safari Technology Preview on macOS Mojave Developer Beta 2 will need to login to websites when restarting the application, or may require logging in again on some websites when launching a new window

Intelligent Tracking Prevention 2.0

  • Enabled the latest version of Safari’s privacy protection “Intelligent Tracking Prevention.” For technical details, see the WebKit blog post.

Web Animations

  • Enabled Web Animations as an experimental feature by default (r232186)
  • Added support for handling relative length units such as em, vw, and vh (r232255)
  • Fixed a bug causing WebAnimation objects to never get destroyed (r232185)

Payment Request

  • Removed currencySystem member (r232155)


  • Added Symbol.prototype.description getter (r232404)
  • Implemented + and - unary operation for BigInt (r232232)
  • Implemented support for % operation for BigInt (r232295)
  • Implemented support for < and > relational operation for BigInt (r232273)
  • Implemented support for =< and >= relational operation for BigInt (r232386)
  • Implemented support for addition operations for BigInt (r232449)
  • Fixed the Array.prototype.concat fast case when a single argument is a Proxy object (r232261)
  • Fixed Date.parse() to properly handle input outside of ES spec limits (r232122)
  • Fixed Array.prototype.sort to reject null comparator (r232666)
  • Renamed Array#flatten to flat (r232226)


  • Fixed not displaying spelling errors in the middle of an inserted paragraph (r232530)

Storage Access API

  • Changed Storage Access API calls to handle the absence of an attached frame (r232584)


  • Enabled Cross-Origin-Resource-Policy by default (r232311)
  • Changed the NetworkCORSPreflightChecker to set the preflight request User-Agent header (r232470)
  • Changed Accept request header values to be more tightly checked in the case of a CORS load (r232728)
  • Fixed the Referrer-Policy response header to not be ignored (r232310)
  • Renamed Cross-Origin-Options HTTP header to Cross-Origin-Window-Policy (r232499)
  • Renamed Cross-Origin-Resource-Policy:same to same-origin (r232309)
  • Migrated From-Origin to Cross-Origin-Resource-Policy (r232217)

Service Workers

  • Added Accept-Encoding:identity to Range requests (r232571)
  • Fixed ServiceWorker registration to store any script fetched through importScripts (r232516)
  • Fixed HTTP Header values validation to not be too strict (r232572)
  • Improved error messages when FetchEvent.respondWith has a rejected promise (r232739)
  • Prevented starting service worker fetch when there is substitute data (r232580)
  • Updated Fetch code to provide more useful exception messages (r232484)


  • Fixed page reloading when viewing photos in Google Drive due to exceeding canvas memory limits (r232113)
  • Fixed memory management when zooming and scrolling on some websites (r232356)
  • Link drag image is inconsistently unreadable in dark mode (r232731)


  • Added an option to restrict communication to localhost sockets (r232420)


  • Changed PopStateEvent to not be cancelable by default (r232610)


  • Changed media elements outside of fullscreen to not be considered main content (r232300)
  • Changed to exit fullscreen when JavaScript alerts are presented (r232437)
  • Changed automatic picture-in-picture to use the main content heuristic (r232301)
  • Changed to stop playing in the background when automatic picture-in-picture is disabled (r232426)
  • Enabled subsampling for progressive JPEG images (r232177)
  • Fixed incorrectly sized captions in picture-in-picture mode (r232220)
  • Fixed regions outside of the fullscreen window becoming exposed during zoom operations (r232543)
  • Fixed fullscreen element clipping by an ancestor (r232208)

Web Inspector

  • Added Same-Site cookie annotations (r232318)
  • Fixed copying a link address in the Elements tab (r232481)
  • Fixed popovers getting dismissed while attempting to move the cursor inside (r232189)
  • Fixed the tab picker becoming briefly visible when the TabBar is initially shown (r232524)
  • Prevented text in “Add New Class” from being auto-capitalized (r232518)


  • Exposed the <link> rel attribute to voiceover (r232326)
  • Fixed VoiceOver to announce when a details element is expanded when using role group (r232285)
  • Fixed setValue on contenteditable to preserve whitespace (r232120, r232259)
  • Fixed VoiceOver to announce fieldset description from aria-describedby when focusing inputs (r232331)
  • Implemented support for new blockquote, caption, and paragraph ARIA roles (r232508)

iCloud Keychain Password Manager

  • Added support for loading when a user indicates they’d like to change a password that is reused in Safari’s Passwords preferences, falling back to loading if that load fails

June 20, 2018 04:00 PM

June 06, 2018

Safari Technology Preview 58, with Safari 12 Features, is Now Available

Surfin’ Safari

Safari Technology Preview Release 58 is now available for download for macOS High Sierra. With this release, Safari Technology Preview is now available for betas of macOS Mojave. If you already have Safari Technology Preview installed on macOS High Sierra, you can update from the Mac App Store’s Updates tab.

This release covers the same revisions of WebKit from Safari Technology Preview 57, but includes new Safari and WebKit features that will be present in Safari 12. The following Safari 12 features are new to Safari Technology Preview 58:

Icons in Tabs. You can enable showing website icons in tabs in Safari’s Tabs preferences.

Automatic Strong Passwords. Safari automatically generates strong, unique passwords when signing up for accounts or changing passwords on websites. New to Safari 12 and Safari Technology Preview 58, generated passwords can be customized using the passwordrules attribute. See Apple’s Password Rules Validation Tool for more information.

Many more WebKit features in Safari 12 are present in this release of Safari Technology Preview and have been in past releases. You can read more about these changes and many others in What’s New in Safari 12.

June 06, 2018 05:00 PM

June 04, 2018

Michael Catanzaro: Security vulnerability in Epiphany Technology Preview

Igalia WebKit

If you use Epiphany Technology Preview, please update immediately and ensure you have revision 3.29.2-26 or newer. We discovered and resolved a vulnerability that allowed websites to access internal Epiphany features and thereby exfiltrate passwords from the password manager. We apologize for this oversight.

The unstable Epiphany 3.29.2 release is the only affected release. Epiphany 3.29.1 is not affected. Stable releases, including Epiphany 3.28, are also not affected.

There is no reason to believe that the issue was discovered or exploited by any attackers, but you might wish to change your passwords if you are concerned.

By Michael Catanzaro at June 04, 2018 11:00 PM

Intelligent Tracking Prevention 2.0

Surfin’ Safari

Today we’re happy to bring you Intelligent Tracking Prevention 2.0, or ITP 2.0. It builds upon ITP 1.0, which we released last year, and ITP 1.1, which was released in March, adding the Storage Access API.

Removal of the 24 Hour Cookie Access Window

ITP 2.0, as opposed to earlier versions, immediately partitions cookies for domains determined to have tracking abilities. The previous general cookie access window of 24 hours after user interaction has been removed. Instead, authenticated embeds can get access to their first-party cookies through the Storage Access API. The API requires that the user interacts with the embedded content.

0 days: Cookies are partitioned and not persisted in 3rd-part contexts. | 30 days: Existing cookies are purged. New cookies are blocked. | Days of use after the most recent interaction with the website or successful use of the Store Access API.

video.example offers an ad-free subscription service and has many of its videos embedded on other websites. ITP classifies video.example as having tracking abilities and therefore partitions its cookies. This is a timeline of how ITP might work for video.example:

  1. Day 1: The user logs in to video.example which updates video.example’s user interaction timestamp.
  2. Day 22: The user clicks to watch a video.example clip on news.example and the embedded video calls the Storage Access API. ITP notes that the user has not previously granted video.example access to its first-party cookies on news.example and thus prompts the user. The user grants storage access and video.example’s user interaction timestamp is updated.
  3. Day 26: The user clicks to watch another video.example clip on news.example and the video.example embed calls the Storage Access API. ITP notes that the user has previously granted video.example access to its first-party cookies on news.example and thus provides access without a prompt and updates video.example’s user interaction timestamp.
  4. Day 55: The user interacts with video.example as first party website which updates video.example’s user interaction timestamp.
  5. Day 76: The user clicks to watch a video.example clip on blog.example and the video.example embed calls the Storage Access API. ITP notes that the user has not previously granted video.example access to its first-party cookies on blog.example and thus prompts the user. The user grants storage access and video.example’s user interaction timestamp is updated.
  6. Day 80-82: The user doesn’t use Safari which means that these three days do not count towards the 30 days before website data purge.
  7. Day 109: video.example’s cookies, website data, and granted storage access entries are purged as a result of 30 days of Safari usage without an update to video.example’s user interaction timestamp.
Developer Advice

If you are a provider of authenticated third-party content, you should adopt the Storage Access API. If your website relies on a third party domain for user authentication, your authentication provider should adopt the Storage Access API or transfer authentication tokens to you in URLs.

User Prompt For the Storage Access API

ITP 2.0 adds a prompt to WebKit’s implementation of the Storage Access API. If the user allows access, their choice is persisted. If the user declines, their choice is not persisted which allows them to change their mind if they at a later point tap a similar embedded widget that calls the Storage Access API.

As an example, video.example may have an ad-free subscription service and have many of its videos embedded on other websites. ITP will thus classify video.example as having tracking abilities and partition its cookies. When the user taps or clicks to play a clip embedded on news.example, video.example can call the Storage Access API to check whether the user is a subscriber. The user will be prompted if they have not explicitly allowed access under news.example previously.

Storage Access API promptStorage Access API Prompt

This prompt provides users with a way to show intent (the tap/click enabling the API call) and provide consent (“Allow” in the prompt). If the user chooses “Allow,” their choice is persisted and subsequent calls to the Storage Access API by video.example embeds on news.example do not trigger a prompt. Instead a tap or click on the embed is enough for a successful API call. As always, ITP considers the eTLD+1 to be the “party,” so a user “Allow” for under will be valid for video.example and any of its subdomains under news.example or any of its subdomains.

Successful use of the Storage Access API now counts as user interaction with the third-party and refreshes the 30 days of use before ITP purges the third-party’s website data. By successful use we mean the user was either prompted right now and chose “Allow,” or had previously chosen “Allow.” The fact that successful Storage Access API calls now count as user interaction allows users to stay logged into services they rarely use as first party but keep using as embedded third parties.

Finally, we received developer feedback (thank you), saying it should be possible to do a popup should storage access be granted but it turns out the user is not logged in. Our original version of the Storage Access API would consume the user gesture and thus require another tap or click to do a login popup. Now, the third-party embed is allowed to do a popup in the resolve scope of the returned promise, like so:

function makeRequestWithUserGesture() {
  var promise = document.requestStorageAccess();
    function () {
      // Storage access was granted.
      // Check whether the user is logged in.
      // If not, do a popup to log the user in.
    function () {
      // Storage access was denied.
<button onclick="makeRequestWithUserGesture()">Play video</button>
Developer Advice

We encourage you to adopt the Storage Access API if you provide authenticated embeds. The API’s prompt provides you with a way to extend your users’ authenticated sessions if ITP has classified your domain as having the ability to track the user. If ITP classifies your domain and you don’t adopt the API, your domain will be permanently blocked from accessing its first-party cookies in a third-party context.

Temporary Compatibility Fix: Automatic Storage Access for Popups

Many federated logins send authentication tokens in URLs or through the postMessage API, both of which work fine under ITP 2.0. However, some federated logins use popups and then rely on third-party cookie access once the user is back on the opener page. Some instances of this latter category stopped working under ITP 2.0 since domains with tracking abilities are permanently partitioned.

Our temporary compatibility fix is to detect such popup scenarios and automatically forward storage access for the third party under the opener page. Since popups require user interaction, the third party could just as well had called the Storage Access API instead.

Developer Advice

If you provide federated login services, we encourage you to first call the Storage Access API to get cookie access and only do a popup to log the user in or acquire specific consent. The Storage Access API provides a better user experience without new windows and navigations. We’d also like to stress that the compatibility fix for popups is a temporary one. Longterm, your only option will be to call the Storage Access API.

Protection Against First Party Bounce Trackers

ITP 2.0 has the ability to detect when a domain is solely used as a “first party bounce tracker,” meaning that it is never used as a third party content provider but tracks the user purely through navigational redirects.

Say the user clicks on a news.example link on the social.example website. Instead of navigating them straight to their destination news.example, they are rapidly navigated through trackerOne.example and trackerTwo.example before reaching news.example. Those two tracker domains can store information about the user’s browsing history in first party storage and cookies. ITP 2.0 detects such tracking behavior and treats those domains just like any other tracker, i.e. purges their website data.

First-party cookie bounce diagram

Protection Against Tracker Collusion

Through our research, we found that cross-site trackers help each other identify the user. This is basically one tracker telling another tracker that “I think it’s user ABC,” at which point the second tracker tells a third tracker “Hey, Tracker One thinks it’s user ABC and I think it’s user XYZ.” We call this tracker collusion, and ITP 2.0 detects this behavior through a collusion graph and classifies all involved parties as trackers.

Cross-site tracker collusion diagram

In the graph above, as soon as trackerSix.example is classified by ITP, all the domains that have redirected to trackerSix.example get classified too. That’s trackerTwo.example, trackerThree.example, and trackerFive.example. Then domains that have redirected to those get classified too, which covers the last two—trackerOne.example and trackerFour.example.

Developer Advice

Avoid making unnecessary redirects to domains that are likely to be classified as having tracking ability.

Origin-Only Referrer for Domains Without User Interaction

ITP’s purging of website data does not prevent trackers from receiving the so called referrer header which reveals the webpage the user is currently on. In ITP 2.0, the referrer, if there is one, is downgraded to just the page’s origin for third party requests to domains that have been classified as possible trackers by ITP and have not received user interaction.

Here’s an example of what we mean by this: Say the user visits https://store.example/baby-products/strollers/deluxe-navy-blue.html, and that page loads a resource from trackerOne.example. Before ITP 2.0, the request to trackerOne.example would contain the full referrer “https://store.example/baby/strollers/deluxe-stroller-navy-blue.html” which reveals a lot about the user to the third-party. With ITP 2.0, the referrer will be reduced to just “https://store.example/”.

For further reading on this subject, see Mozilla’s research on origin-only referrers.


Does ITP differentiate between my subdomains?
No. ITP captures statistics and applies its rules for the effective top-level domain plus one, or eTLD+1. An eTLD is .com or so an example of an eTLD+1 would be but not (eTLD+2) or just (eTLD).

Does eTLD mean public suffix?
Yes. See the Public Suffix List.

Is there a way for users to whitelist my domain to be excepted from ITP’s rules?
No, there is no such whitelisting feature.

How does ITP classify a domain’s tracking abilities?
See the original ITP 1.0 blog post for details on the machine learning model.

My domain is not a tracker, but it gets classified by ITP. Is that a bug?
ITP does not rely on a centralized blacklist of known trackers. Instead, it captures per-domain (eTLD+1) statistics on-device and classifies each domain’s ability to track cross-site. If a domain has the ability to track the user cross-site, it’s subject to ITP’s cookie and website data rules.

Is it enough for users to visit my website to keep its cookies from being purged if my domain gets classified by ITP?
No, a mere visit does not suffice. The user has to interact with your website, meaning a tap, click, or form entry. In ITP 2.0, user granted access through the Storage Access API also counts as such user interaction.

How do I reset ITP or the domains I’ve allowed storage access for?
Clear your Safari history. Note that this gets rid of data that may be needed to reproduce an ITP issue. If you’re investigating a bug related to ITP, don’t clear your history before you’re done with that work.

I need to debug my website in regards to ITP. Are there specific developer tools?
We’re working on an ITP Debug Mode which will help you debug websites and capture data that’s useful when filing bugs on ITP. It will be announced on this blog.

What is an authenticated widget, an authenticated embed, or authenticated third-party content?
The web platform allows for powerful integration across websites. This enables services such as social media to create widgets that are to be embedded as third-party content on news sites and blogs, but it also enables cross-site tracking. Some widgets have to see the user as logged in to work. For example, if the user wants to comment on blog.example with their social.example account, the social.example commenting widget needs to see the user as logged in to their service. We refer to these widgets as authenticated and to enable them while disabling cross-site tracking, the widgets now have to ask for permission to see the user’s identity, per-site.

How does the removal of the 24 hour cookie access window prevent cross-site tracking from social media etc?
ITP 1.0 had a 24 hour window in which websites the user interacted with could use their cookies as in previous versions of Safari. This was a compatibility measure we took to enable federated logins (e.g. use social.example to login to news.example) and authenticated third-party content (e.g. use social.example to make a comment on blog.example). However, this also allowed social media and search engines that the user interacted with as first parties to track the user across websites while inside that 24 hour window. The mere existence of third-party content from these services was enough for them to see which webpages the user visited. For example, if a user used social.example and then, several hours later, visited news.example which had a social.example Like button or comment widget embedded on the site, social.example could track their browsing on news.example. In ITP 2.0 we restrict such third-party content to only be able to identify the user when they actually use the content, such as write a comment or play a video. This is also the point at which Safari will ask for the user’s permission (if the widget is asking for permission to see its cookies).

Feedback and Bug Reports

Please report bugs through and send feedback to our evangelist Jon Davis. If you have technical questions on how the feature works you can find me on Twitter @johnwilander.

June 04, 2018 07:00 PM

May 30, 2018

Release Notes for Safari Technology Preview 57

Surfin’ Safari

Safari Technology Preview Release 57 is now available for download for macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 231553-232108.

This version of Safari Technology Preview will no longer run on macOS Sierra. To continue testing or living on the latest enhancements to Safari and WebKit, please upgrade to macOS High Sierra.


  • Added support for Intl.NumberFormat().formatToParts() (r231867)
  • Changed to throw SyntaxErrors for runtime generated regular expressions with errors (r231939)
  • Implemented BigInt support for *, /, and == operations (r231733, r231886, r231629)
  • Improved specification compliance for Internationalization APIs (r231740)
  • Improved the speed of Object.assign for final objects (r231687)


  • Exposed Web Animations CSS integration as an experimental feature (r231798)
  • Fixed a bug where animation-play-state:paused causes very high cpu load because of a style invalidation loop (r231794)

Storage Access API

  • Extended the lifetime of cookies on successful user approval (r231684)


  • Added initial support for the Cross-Origin-Options HTTP response header (r231622, r231654)
  • Changed Cross-Origin-Options:deny and Cross-Origin-Options:allow-postmessage to prevent getting navigated by cross-origin scripts (r231911)
  • Changed X-Frame-Options:SAMEORIGIN to check all ancestor frames (r231730)


  • Enabled the modern EME API by default (r231903)
  • Fixed media continuing to load after rendered invisible (e.g. removed from DOM; scrolled off screen) (r231817)
  • Improved NowPlaying using the element "title" attribute when available (r231866)


  • Changed the accessiblility name provided for a node to simplify the whitespace when using innerText (r231627)
  • Excluded hidden nodes which are not directly referenced from participating in name or description content (r231620)
  • Ensured listbox and combobox roles embedded in labels participate in name calculation (r231778)
  • Exposed the primary screen height through the AX API (r231937)
  • Fixed a bug with VoiceOver causing <iframe> scrolling focus jumping (r231628)
  • Fixed VoiceOver to manually focus or read dialog paragraph description text inside the modal in role=dialog elements with aria-modal=true (r231720)


  • Fixed a crash that happens if a browsing context’s cookies are requested prior to an initial navigation (r232031)
  • If the network or storage process crashes, terminate the automation session to avoid undefined behavior (r232028)
  • Automation.getBrowsingContext now returns the same window origin as window.screenX and window.screenY (r231769)

Web Inspector

  • Added rulers and guides to the Canvas tab (r231819, r231881)
  • Changed the Canvas tab to not automatically select a recording when viewing a canvas (r231773)
  • Improved the placement logic for the element details popover that is shown during Inspect Element mode (r231838)
  • Calculating the visual effect of each Canvas action is now off by default for performance reasons. (r231981)

May 30, 2018 05:00 PM

May 27, 2018

Michael Catanzaro: Thoughts on Flatpak after four months of Epiphany Technology Preview

Igalia WebKit

It’s been four months since I announced Epiphany Technology Preview — which I’ve been using as my main browser ever since — and five months since I announced the availability of a stable channel via Flatpak. For the most part, it’s been a good experience. Having the latest upstream development code for everything is wonderful and makes testing very easy. Any user can painlessly download and install either the latest stable version or the bleeding-edge development version on any Linux system, regardless of host dependencies, either via a couple clicks in GNOME Software or one command in the terminal. GNOME Software keeps it updated, so I always have a recent version. Thanks to this, I’m often noticing problems shortly after they’re introduced, rather than six months later, as was so often the case for me in the past. Plus, other developers can no longer complain that there’s a problem with my local environment when I report a bug they can’t reproduce, because Epiphany Technology Preview is a canonical distribution environment, a ground truth of sorts.

There have been some rough patches where Epiphany Technology Preview was not working properly — sometimes for several days — due to various breaking changes, and the long time required to get a successful SDK build when it’s failing. For example, multimedia playback was broken for all of last week, due to changes in how the runtime is built. H.264 video is still broken, since the relevant Flatpak extension is only compatible with the 3.28 runtime, not with master. Opening files was broken for a while due to what turned out to be a bug in mutter that was causing the OpenURI portal to crash. I just today found another bug where closing a portal while visiting Slack triggered a gnome-shell crash. For the most part, these sorts of problems are expected by testers of unstable nightly software, though I’m concerned about the portal bugs because these affect stable users too. Anyway, these are just bugs, and all software has bugs: they get fixed, nothing special.

So my impression of Flatpak is still largely positive. Flatpak does not magically make our software work properly in all host environments, but it hugely reduces the number of things that can go wrong on the host system. In recent years, I’ve seen users badly break Epiphany in various ways, e.g. by installing custom mimeinfo or replacing the network backend. With Flatpak, either of these would require an incredible amount of dedicated effort. Without a doubt, Flatpak distribution is more robust to user error. Another advantage is that we get the latest versions of OS dependencies, like GStreamer, libsoup, and glib-networking, so we can avoid the many bugs in these components that have been fixed in the years since our users’ LTS distros froze the package versions. I appreciate the desire of LTS distros to provide stability for users, but at the same time, I’m not impressed when users report issues with the browser that we fixed two years ago in one dependency or another. Flatpak is an excellent compromise solution to this problem: the LTS distro retains an LTS core, but specific applications can use newer dependencies from the Flatpak runtime.

But there is one huge downside to using Flatpak: we lose crash reports. It’s at best very difficult — and often totally impossible — to investigate crashes when using Flatpak, and that’s frankly more important than any of the gains I mention above. For example, today Epiphany Technology Preview is crashing pretty much constantly. It’s surely a bug in WebKit, but that’s all I can figure out. The way to get a backtrace from a crashing app in flatpak is to use coredumpctl to manually dump the core dump to disk, then launch a bash shell in the flatpak environment and manually load it up in gdb. The process is manual, old-fashioned, primitive, and too frustrating for me by a lot, so I wrote a little pyexpect script to automate this process for Epiphany, thinking I could eventually generalize it into a tool that would be useful for other developers. It’s a horrible hack, but it worked pretty well the day I tested it. I haven’t seen it work since. Debuginfo seems to be constantly broken, so I only see a bunch of ???s in my backtraces, and how are we supposed to figure out how to debug that? So I have no way to debug or fix the WebKit bug, because I can’t get a backtrace. The broken, inconsistent, or otherwise-unreliable debuginfo is probably just some bug that will be fixed eventually (and which I half suspect may be related to our recent freedesktop SDK upgrade. Update: Alex has debugged the debuginfo problem and it looks like that’s on track to be solved), but even once it is, we’re back to square one: it’s still too much effort to get the backtrace, relative to developing on the host system, and that’s a hard problem to solve. It requires tools that do not exist, and for which we have no plans to create, or even any idea of how to create them.

This isn’t working. I need to be able to effortlessly get a backtrace out of my application, with no or little more effort than running coredumpctl gdb as I would without Flatpak in the way. Every time I see Epiphany or WebKit crash, knowing I can do nothing to debug or investigate, I’m very sorely tempted to switch back to using Fedora’s Epiphany, or good old JHBuild. (I can’t promote BuildStream here, because BuildStream has the same problem.)

So the developer experience is just not good, but set that aside: the main benefits of Flatpak are for users, not developers, after all. Now, what if users run into a crash, how can they report the bug? Crash reports are next to useless without a backtrace, and wise developers refuse to look at crash reports until a quality backtrace has been posted. So first we need to fix the developer experience to work properly, but even then, it’s not enough: we need an automatic crash reporter, along the lines of ABRT or apport, to make reporting crashes realistically-achievable for users, as it already is for distro-packaged apps. But this is a much harder problem to solve. Such a tool will require integration with coredumpctl, and I have not the faintest clue how we could go about making coredumpctl support container environments. Yet without this, we’re asking application developers to give up their most valuable data — crash reports — in order to use Flatpak.

Eventually, if we don’t solve crash reporting, Epiphany’s experiment with Flatpak will have to come to an end, because that’s more important to me than the (admittedly-tremendous) benefits of Flatpak. I’m still hopeful that the ingenuity of the Flatpak community will find some solutions. We’ll see how this goes.

By Michael Catanzaro at May 27, 2018 11:39 PM

May 16, 2018

Release Notes for Safari Technology Preview 56

Surfin’ Safari

Safari Technology Preview Release 56 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 230913-231553.

This is the last release of Safari Technology Preview that will install and run on macOS Sierra. To continue testing or living on the latest enhancements to Safari and WebKit, please upgrade to macOS High Sierra.


  • Implemented Intl.PluralRules (r231047)


  • Added support for stream APIs (r231194)


  • Fixed event listener removal to be immediate (r231248)
  • Fixed DHTML drag operations to report the number of files in the operation (r231003)
  • Fixed window.postMessage(), window.focus(), and window.blur() unexpectedly throwing a TypeError (r231037)
  • Serialized font-variation-settings with double-quotes to match standards (r231165)
  • Stopped using the id of an <iframe> as fallback if its name attribute is not set (r231456)


  • Added support for the WHATWG proposed From-Origin:same and From-Origin:same-site response headers with nested frame origin checking as an off by default experimental feature (r230968)
  • Fixed CSP referrer for a document blocked due to a violation of its frame-ancestors directive (r231461)
  • Fixed CSP status-code for a document blocked due to a violation of its frame-ancestors directive (r231464)
  • Fixed CSP to pass the document’s referrer (r231445)
  • Fixed CSP to only notify Web Inspector to pause the debugger on the first policy to violate a directive (r231443)
  • Fixed a bug causing first-party cookies to be blocked on redirects (r231008)


  • Fixed CSS filters which reference SVG filters to respect the color-interpolation-filters of the filter (r231473)
  • Fixed feTurbulence to render correctly on a Retina display (r231485)
  • Fixed shape-outside and filter styles occuring twice in the result of getComputedStyle (r230976)


  • Changed font collection fragment identifiers to use PostScript names (r231259)
  • Fixed selecting text on a webpage causing the text vanish (r231178)
  • Fixed hiding then showing an <object> of type image to ensure the underlying image is displayed (r231292)


  • Changed MediaStreams that are playing to allow removing some of its tracks (r231304)
  • Updated text track cue logging to include cue text (r231490)

Web Inspector

  • Improved the user experience in Canvas tab to show progress bars while processing actions in a new recording (r231218)
  • Ensured that tabbing through the last section of rules in the Styles editor wraps back to the first section of rules (r231372)
  • Fixed Console drawer resizing when the console prompt has more than one line of code (r231527)
  • Fixed unsupported properties that sometimes don’t get warnings just after adding them (r231377)
  • Updated the Canvas tab to determine functions by looking at the prototype (r231368)

May 16, 2018 05:00 PM

May 02, 2018

Release Notes for Safari Technology Preview 55

Surfin’ Safari

Safari Technology Preview Release 55 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 230521-230913.


  • Added support for calc() in webkit-gradient and cross-fade (r230816)
  • Changed :active pseudo class to deactivate when using pressure sensitive trackpad (r230786)
  • Omitted the default value when serializing font-feature-settings (r230838)
  • Updated HSL and HSLA parsing to match CSS Color 4 (r230861)


  • Enforced content-type for <script> tags (r230602)
  • Fixed input.webkitEntries to work as expected when a folder contains accented chars (r230639)
  • Setting event.returnValue to true is now a no-op (r230664)


  • Fixed animated GIFs with finite looping to loop the expected number of times (r230712)
  • Fixed the position of the caret in empty table cells (r230797)


  • Added the accessibility events to the HTML attribute names so AOM works with DOM Level 1 events (r230890)
  • Fixed a hang when triggering an alert from an AOM increment event (r230782)


  • Fixed function.prototype.caller to not return generator bodies (r230662)

Web Driver

  • Fixed simulated mouse interactions to not be done until the associated DOM events have been dispatched (r230817)

Web Inspector

  • Fixed selecting and copying text from a Network tab popover (r230701)


  • Added allSamplesInTrackEnqueued event (r230909)


  • Fixed a WebRTC data channel issue for non-ASCII characters. (r230524)


  • Changed to use CSP and content blockers for sync XHR (r230810)

Bug Fixes

  • Fixed an issue that would sometimes incorrectly rule out PDF as a mime type that can be showed (r230853)
  • Fixed an issue with Command-clicking web app links on (r230721)

May 02, 2018 05:00 PM

April 27, 2018

Visualizing Layers in Web Inspector

Surfin’ Safari

Recent releases of Safari Technology Preview contain a new experimental feature for Web Inspector: the Layers tab. Building upon the legacy Layers sidebar, this tab introduces a 3D visualization of the inspected page’s compositing layers, to provide developers with a more hands-on (and hopefully fun!) way to understand where layers are being generated and in what order they will render.

Layers tab

In this post, we’ll look at how the Layers tab can be used to find unexpected memory consumption or excessive repaints on a web page.

A Whirlwind Introduction to Layers

Before introducing any debugging tool, it’s important to clarify what we’re aiming to debug in the first place. At first glance, a layer visualization may appear quite similar to a DOM visualization (such as Firefox’s Tilt), yet compositing layers and DOM elements are conceptually different entities. While web developers are intimately familiar with the DOM tree as the structure of elements on a page, the way in which these elements end up rendered on screen tends to only be learned as a need arises.

DOM elements are not just painted to the screen one by one. After the position and size of each element has been calculated, they are drawn onto a series of surfaces called layers. It is these layers which are then composited in a particular order to produce the resulting appearance of the web page. All pages have a root layer corresponding to the document itself, but any DOM element can cause a new layer to be created. Among the reasons for this are element type (e.g. <canvas>), presence of certain CSS properties (e.g. 3D transforms), or interaction with other layer-generating elements.

Layers have a significant impact on rendering performance. Without layers, animating any element (e.g. sliding a header down) would mean having to wastefully repaint the whole page on every frame. If the element has its own layer, however, it may be possible to skip repainting altogether and animate by simply recompositing the layers on screen. Of course, the trade-off for this computational savings is memory cost. Creating too many layers—intentionally or otherwise—can have disastrous results on memory-constrained devices. Like any performance concern, finding the right balance is an empirical issue, so having a suitable debugging tool is crucial!

Identifying Compositing Issues with the Layers Tab

The Layers tab features two real-time representations of the layers on the page, a 3D visualization and a data table. We can use these in conjunction to discover potential performance problems.

We might begin by exploring the visualization to understand each layer’s position, size, and rendering order. To navigate, use left-drag to rotate, right-drag to pan, and scroll to zoom. Clicking a layer in the visualization highlights the corresponding row in the layer table.

We can then use the table to identify the costliest layers, sorting by Memory to prioritize memory consumption (default) or by Paints to prioritize repaint count. Selecting a row in the table displays information about why the layer exists as well as its composited and visible dimensions (visualized as an outline and a plane, respectively). This also recenters the visualization on the selection, clarifying how that layer fits into the larger picture.

explore table

At this point, perhaps we’ll take notice of an oddly-positioned layer nearby and jump to it accordingly. Or we could simply inspect each of the most expensive layers in turn. If a layer seems suspicious, we can click the arrow icon in its table row to switch to the Elements tab and examine the DOM element that generated it. And if that’s not enough to explain an unusually high repaint count, we can turn to the Timelines tab to figure out where those paint events are being triggered.

Once we’ve identified our issue, it’s just a matter of making the appropriate HTML/CSS modifications!


The Layers tab is available in the latest Safari Technology Preview. To enable it, visit the Experimental panel on Web Inspector’s Settings tab and check the “Enable Layers tab” setting. Give it a try and let us know what you think! Reach out at #webkit-inspector on Freenode IRC, to @webkit on Twitter, or by filing a bug.

April 27, 2018 05:00 PM

April 25, 2018

Web Inspector Styles Sidebar Improvements

Surfin’ Safari

In Web Inspector that recently shipped with Safari 11.1 on macOS High Sierra, the Elements tab sidebar panels and the styles editor got a lot of attention from the Web Inspector team. We’ve re-written the styles editor to provide an editing experience more familiar to web developers, and rearranged the sidebar panels to improve access to the most used tools. The design refresh brings new behaviors and fine-tuning to enhance web developers’ ability to access and understand the elements they’re inspecting.

Tabs Layout

styles tabs before & afterBefore / After

In the Elements tab, Styles and Computed are the most commonly used panels. We made them top-level tabs, so it takes a single click to switch between them.

Styles Panel

styles panel information density before & afterBefore / After

The redesigned Styles panel of the same size now fits more data:

  • Selectors are no longer generated for style attributes
  • The default “Media: all” header is no longer shown
  • The icons were removed to save some horizontal space

Syntax Highlighting

styles syntax highlighting

Property values are now black to make them easier to distinguish from property names. Strings are still red, but links are now blue.

We added curly braces back so copying CSS would produce valid CSS. Curly braces, colons, and semicolons are light gray so they won’t distract from the content.

Styles Editor

We rewrote the styles editor from scratch. This is the first major overhaul of the styles editor since 2013. Instead of a free-form text editor, we changed to cell-based style editing.

Styles tab and shift-tab behavior

CSS property names and values are now separate editable fields. Pressing Tab (⇥) or Return navigates to the next editable field. Pressing Shift-Tab (⇧⇥) navigates to the previous editable field.

Also, typing a colon (“:”) when focused on the property name focuses on the corresponding property value. Typing semicolon (“;”) at the end of the property value navigates to the next property.

Styles add new property behavior

To add a new property, you can click on the white space before or after an existing property. Pressing Tab (⇥) or Return when focused on the last property value also adds a new property.

Styles remove property behavior

To remove a property, you can remove either a property name or a property value.

Styles up and down arrow behavior

Completion suggestions display right away when focused on the value field. Completion values apply right away when selecting using Up and Down arrow keys.

Styles more arrow key behaviors

While editing a property field, Up and Down arrow keys now can increment and decrement values. You can change the interval by holding modifier keys:

  • Option (⌥): 0.1
  • Shift (⇧): 10
  • Command (⌘): 100

Legacy Settings

Legacy settings screen with the Legacy Style Editor setting

The previous version of the styles editor is still available in the in Web Inspector settings, but it’s no longer maintained.

The Visual Styles Panel never gained enough traction to remain in Elements tab by default. It is no longer maintained. Along with the Legacy Style Editor, the Visual Styles Panel can still be enabled in the Experimental settings.


Please report bugs and feature requests regarding the new styles editor on If you’re interested in contributing or have any questions, please stop by the #webkit-inspector IRC channel.

Web Inspector is primarily written in HTML, JavaScript, and CSS, which means that web developers already have the skills needed to jump in and contribute a bug fix, enhancement or a new feature.

April 25, 2018 05:00 PM

April 18, 2018

Release Notes for Safari Technology Preview 54

Surfin’ Safari

Safari Technology Preview Release 54 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 230029-230521.

Clipboard API

  • Fixed copying a list from Microsoft Word to TinyMCE when mso-list is the first property (r230120)
  • Prioritized file promises over filenames during drag and drop (r230221)

Beacon API

  • Fixed Beacon redirect responses to be CORS validated (r230495)


  • Implemented createImageBitmap(Blob) (r230350)


  • Added a special software encoder mode when a compression session is not using a hardware encoder and VCP is not active (r230451)
  • Added experimental support for MDNS ICE candidates in WebRTC data channel peer-to-peer connections (r230290, r230307)

Web Inspector

  • Fixed the errors glyph to fully change to blue when active (r230372)
  • Tinted all pixels drawn by a shader program when hovering over a tree element in the Canvas Tab (r230127)

April 18, 2018 05:00 PM

April 15, 2018

Manuel Rego: CSSWG F2F Berlin 2018

Igalia WebKit

Last week I was in Berlin for the CSS Working Group (CSSWG) face-to-face meeting representing Igalia, member of the CSSWG since last year. Igalia has been working on the open web platform for many years, where we help our customers with the implementation of different standards on the open source web engines. Inside the CSSWG we play the implementors role, providing valuable feedback around the specifications we’re working on.

It was really nice to meet all the folks from the CSSWG there, it’s amazing to be together with such a brilliant group of people in the same room. And it’s lovely to see how easy is to talk with any of them, you all rock!

CSSWG F2F Berlin 2018 by Rossen Atanassov CSSWG F2F Berlin 2018 by Rossen Atanassov

This is a brief post about my highlights from there, of course totally subjective and focused on the topics I’m more interested.

CSS Grid Layout

We were discussing two issues of the current specification related to the track sizing algorithm and its behavior in particular cases. Some changes will be added in the specification to try to improve them and we’ll need to update the implementations accordingly.

On top of that, we discussed about the Level 2 of the spec. It’s already defined that this next level will include the following features:

  • The awaited subgrids feature: There was the possibility of allowing subgrids in both axis (dual-axis) or only in one of them (per-axis), note that the per-axis approach covers the dual-axis if you define the subgrid in both axis.

    There are clear uses cases for the per-axis approach but the main doubt was about how hard it’d be to implement. Mats Palmgren from Mozilla posted a comment on the issue explaining that he has just created a prototype for the feature following the per-axis idea, so the CSSWG resolved to remove the dual-axis one from the spec.

  • And aspect-ratio controlled gutters: Regarding this topic, the CSSWG decided to add a new ar unit. We didn’t discuss anything more but we need to decide what we’ll do in the situations where there’s no enough free space to fulfill the requested aspect-ratio, should we ignore it or overflow in that case?

    Talking to Rachel Andrew about the issue, she was not completely sure of what would be the preferred option from the authors point of view. I’ve just added some examples to the issue so we can discuss about them there and gather more feedback, please share your thoughts.


This was a discussion I wanted to have with the CSSWG people in order to understand better the current situation and possible next steps for the CSSWG test suites.

Just to add some context, the CSSWG test suites are now part of the web-platform-tests (WPT) repository. This repository is being used by most browser vendors to share tests, including tests for new CSS features. For example, at Igalia we’re currently using WPT test suites in all our developments.

The CSSWG uses the CSS Test Harness tool which has a build system that adds some special requirements for the test suites. One of them causes that we need to duplicate some files in the repository, which is not nice at all.

Several people in the CSSWG still rely on this tool mainly for two things:

  • Run manual tests and store their results: Some CSS features like media queries or scrolling are hard to automate when writing tests, so several specs have manual tests. Probably WebDriver can help to automate this kind of tests, maybe not all though.
  • Extract status reports: To verify that a spec fulfills the CR exit criteria, the current tooling has some nice reports, it also provides info about the test coverage of the spec.

So we cannot get rid of the CSS Test Harness system at this point. We discussed about possible solutions but none of them were really clear, also note that the lack of funding for this kind of work makes it harder to move things forward.

I still believe the way to go would be to improve the WPT Dashboard ( so it can support the 2 features listed above. If that’s the case maybe the specific CSS Test Harness stuff won’t be needed anymore, thus the weird requirements for people working on the test suites will be gone, and there would be a single tool for all the tests from the different working groups.

As a side note needs some infrastructure improvements, for example Microfost was not happy as Ahem font (which is used a lot in CSS tests suites) is still not installed on the Windows virtual machines that extract test results for

Floats, floats, floats

People are using floats to simulate CSS Shapes on browsers that don’t have support yet. That is causing that some special cases related to floats happen more frecuently, and it’s hard to decide what’s the best thing to do on them.

The CSSWG was discussing what would be the best solution when the non-floated content doesn’t fit in the space left by the floated elements. The problem is quite complex to explain, but imagine the following picture where you have several floated elements.

An example of float layout An example of float layout

In this example there are a few floated elements restricting the area where the content can be painted, if the browser needs to find the place to add a BFC (like a table) it needs to decide where to place it avoiding overlapping any other floats.

There was a long discussion, and it seems the best choice would be that the browser tests all the options and if there’s no overlapping then puts the table there (basically Option 1 in the linked illustration). Still there are concerns about performance, so there’s still more work to be done here. As a result of this discussion a new CSS Floats specification will be created to describe the expected behavior in this kind of scenarios.

Monica Dinculescu created a really cool demo to explain how float layout works, with the help of Ian Kilpatrick who knows it pretty well as he has been dealing with lots of corner cases while working in LayoutNG.


The members of the CSSWG were invited to the co-located TYPO Labs event. I attended on Friday when Elika (fantasai), Myles and Rossen gave a talk. It was nice to see that CSS Grid Layout was mentioned in the first talk of the day, as an useful tool for typographers. Variable fonts and Virtual Reality were clearly hot topics in several talks.

Elika (fantasai), Myles and Rossen in the CSSWG talk at TYPO Labs Elika (fantasai), Rossen and Myles in the CSSWG talk at TYPO Labs

It’s funny that the last time I was in Berlin was 10 years ago for a conference related to TYPO3, totally unrelated but with a similar name. 😄


Some pictures of Berlin Some pictures of Berlin

And that’s mostly all that I can remember now, I’m sure I’m missing many other important things. It was a fantastic week and I even find some time for walking around Berlin as the weather was really pleasant.

April 15, 2018 10:00 PM

April 12, 2018

New WebKit Features in Safari 11.1

Surfin’ Safari

Update: This post has been updated to omit Offscreen Canvas which is not available in Safari 11.1 on macOS and Safari on iOS 11.3. Offscreen Canvas is available as an experimental feature in Safari Technology Preview releases.

The recently shipped Safari 11.1 in macOS High Sierra and Safari on iOS 11.3 includes WebKit improvements that add support for a lot of exciting web platform technologies. These features offer new capabilities to developers to improve user-perceived performance of web content, it adds a new dynamic approach for offline experiences, and brings a standard approach to web payments that simplifies development. It also delivers redesigned developer tools in Web Inspector that improve overall usability and convenience.

What follows is a short tour of all of the new features and improvements available with Safari 11.1.

Service Worker API

The Service Worker API enables scripts that run in the background to handle generalized processing for web pages. Service Worker scripts commonly work with other complimentary APIs, such as the Cache API, also included in this release, to store fetch requests and responses that to improve network performance or provide an offline experience. WebKit’s implementation respects user privacy partitioning Service Workers by the top level document origin to help prevent cross-site tracking.

Read the “Workers at Your Service” blog post for more details about the WebKit implementation of Service Workers.

Payment Request API for Apple Pay

WebKit added support for the Payment Request API to perform Apple Pay transactions. This enables merchants to offer payment methods across multiple browsers using a standard API, greatly reducing the effort of supporting secure payments across different browsers and platforms.

See Introducing the Payment Request API for Apple Pay for more details.

Beacon API

Beacon API schedules asynchronous requests to send before the page is unloaded and completes them without a blocking request. This is useful for sending diagnostics data about the web application without impacting perceived page load performance.

See the Beacon specification for more information.

Directory Upload & Clipboard API Updates

The Clipboard API has a number of improvements focusing on a modernized implementation of the DataTransfer API. It adds support for dataTransfer.items, reading and writing of HTML content and custom MIME types, and fixed a number of bugs including copying & pasting images from native applications. WebKit also added support for uploading directories using DataTransfer.webkitGetAsEntry() and input.webkitdirectory, allowing interoperability with other browsers. Users can now upload an entire directory onto cloud storage and file sharing services such as iCloud or Dropbox.

Read more about the improvements to the Clipboard API and Directory Upload API.

Video as Image Assets

Animated image formats are very popular, but they easily become large, bandwidth intensive file sizes. To address the performance impact, WebKit in Safari now supports loading H.264 encoded MP4 video with an HTML tag. This allows content authors to replace animated GIF files that are much larger than H.264 video files and require more processing power to display. Beyond the performance gains, this change also allows web content authors to use videos as a CSS background-image.

Some detailed information about this change is available in the blog post Evolution of : Gif without the GIF by Colin Bendell.


Page authors have more control over font loading behavior using the newly support font-display descriptor. WebKit’s new default behavior will show invisible text for up to 3 seconds before switching to an installed font until the desired font finishes downloading. Using font-display, the page author can use the swap value to immediately show an installed font until the specified web font is downloaded. There is a fallback behavior to show an installed font for up to 3 seconds and if the desired font doesn’t load in that time, it will never be shown. Finally, the optional behavior will use the font if it is available in the browser’s cache. If it isn’t there, it skips using it at all. These provide a rich set of behaviors for web developers to control the loading and display experience that best suits the design of their web content.

Find more details in the CSS Fonts Module Level 4 specification.

HTML Image Decoding

Content authors sometimes need a loaded, fully decoded image that is available immediately. Loading and decoding large images or lots of images can cause page performance to suffer. The new HTMLImageElement.decode() function asynchronously starts decoding an image and returns a Promise that resolves when the decoded image is available. With it, developers now have control over when loaded images are decoded, without tying up the main thread. Developers can also declaratively indicate an image should load asynchronously using the decoding attribute on an <img> element.

<img decoding="async">
<img decoding="sync">
<img decoding="auto">

For more information, read the WhatWG proposal.

Passive Event Listeners

To avoid causing poor scroll performance when attaching event handlers to touchstart, touchmove, or wheel events, developers can specify their event listener as passive if the listener does not call preventDefault(). This enables Safari to continue to provide high performance scrolling without waiting for the event listener to finish.

More details on Passive Events Listeners can be found in the DOM specification.

Storage Access API

The new Storage Access API provides a solution to allow third-party embeds to request access to their first-party cookies when the user interacts with them in a world with Intelligent Tracking Prevention. This gives content providers the flexibility to provide embedded content, while offering users transparency about who they are sharing their information with.

Find out more about the Storage Access API on the WebKit blog.

Subresource Integrity

WebKit has added support for Subresource Integrity which enables websites to validate the integrity of resources and reject them if something has changed outside the site owner’s control. An integrity check compares a hash provided by the web content author in an integrity attribute on a <script> or a <link> element with a computed hash of the delivered resource. When the hashes don’t match, instead of applying a stylesheet, or executing a script, a network error is returned. This helps web content authors reduce impact a compromised content delivery network (CDN).

Read the Subresource Integrity specification to learn more.

WebDriver Improvements

Safari includes several improvements to the implementation of WebDriver. With Safari 11.1, WebDriver now supports file uploads and testing WebRTC functionality. In addition, several bug fixes improve the overall quality of the WebDriver implementation.

Web Inspector Improvements

Web Inspector has honed the design of several existing tools, and also adds a useful new tool to inspect HTML Canvas elements. The new Canvas tab allows web developers to understand the changes in recorded frames of canvas animations.

The Styles sidebar in the Elements tab was reworked to use a different, but familiar model for editing style rules, properties and values. It also features improvements in navigating between different style views.

Finally, the Network tab was redesigned, improving both the timeline of loading resources, and navigating to the network details of each resource such as content previews, headers, cookies, size and timing details.


Most of these improvements are available to users running iOS 11.3 and macOS High Sierra 10.13.4, as well as macOS Sierra and OS X El Capitan. The Storage Access API is only available on iOS 11.3 and macOS High Sierra 10.13.4. These features were also available to web developers with Safari Technology Preview releases. Changes in this release of Safari were included in the following Safari Technology Preview releases: 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47. Download the latest Safari Technology Preview release to stay on the forefront of future web features. You can also use the WebKit Feature Status page to watch for changes to your favorite web platform features.

We love hearing from you. Send a tweet to @webkit or @jonathandavis to share your thoughts on this release, and any features you were hoping for that didn’t make it. If you run into any issues, we welcome your bug reports for Safari, or WebKit bugs for web content issues.

April 12, 2018 05:00 PM

April 05, 2018

Introducing the Payment Request API for Apple Pay

Surfin’ Safari

We’re pleased to announce that Safari 11.1 on macOS and Safari on iOS 11.3 now support the W3C Payment Request API for conducting Apple Pay transactions on the web.

We first introduced Apple Pay on the Web in macOS Sierra and iOS 10. Apple Pay brought novel ease-of-use, security, and privacy to online transactions, so we’ve been encouraged to see it widely adopted by merchants in the years since. However, we recognize that merchants need to support multiple payment methods, and doing so comes at the cost of increased complexity. Payment Request aims to reduce this complexity by supporting payment methods across multiple browsers using a standard API.

Today I’ll take you step-by-step through an Apple Pay transaction using Payment Request. If you’ve already worked with Apple Pay JS, this should look familiar to you. If you haven’t, this is a great place to get started!


This post assumes that you have already registered a merchant identifier and set up your server environment to process Apple Pay transactions. You can find detailed instructions for doing this in the Apple Pay on the Web documentation.

Showing Apple Pay Buttons

Apple Pay transactions are always initiated by your customer, so you’ll need to display an Apple Pay button for them to tap or click. For a consistent visual appearance, WebKit provides built-in support for rendering Apple Pay buttons. Here’s how to display the most basic type of Apple Pay button:

<button style="-webkit-appearance: -apple-pay-button;"></button>

There are several other types of buttons available in various styles. Here’s a few that you might have seen while shopping in Safari:

Apple Pay Buttons

See Displaying Apple Pay Buttons for more information on the button types and styles available.

According to the Apple Pay on the Web Human Interface Guidelines, you should display Apple Pay buttons whenever your customer is using a supported device. To check if your customer’s device supports Apple Pay, call ApplePaySession.canMakePayments():

if (window.ApplePaySession && ApplePaySession.canMakePayments())
    // Show Apple Pay button.

If your customer taps or clicks an Apple Pay button, you should always present the Apple Pay payment sheet. If they haven’t yet enrolled a payment card you can accept in Apple Pay, Safari prompts them to do so before continuing with your transaction. Since these rules are specific to Apple Pay, Apple Pay JS’s ApplePaySession API is required for this step. The remainder of the transaction can be conducted using standard Payment Request API.

Constructing a PaymentRequest

When your customer taps or clicks an Apple Pay button, you initiate the transaction by constructing a new PaymentRequest:

var request = null;
if (window.PaymentRequest)
    request = new PaymentRequest(methods, details, options);
    // Consider using Apple Pay JS instead.

The PaymentRequest constructor takes three arguments: the payment methods you support, the details to show to your customer (like shipping options and total amount), and any options you require.

Payment Methods

Payment methods represent the means by which you can accept payments from your customer using Payment Request. You specify the payment methods you accept as a sequence of PaymentMethodData dictionaries, each of which contains an identifier (supportedMethods) and associated data.

To use Apple Pay with Payment Request, include it as a payment method. Apple Pay’s URL-based payment method identifier is "", and its associated data is an ApplePayRequest dictionary. Here’s what a PaymentMethodData dictionary for Apple Pay might look like:

const applePayMethod = {
    supportedMethods: "",
    data: {
        version: 3,
        merchantIdentifier: "",
        merchantCapabilities: ["supports3DS", "supportsCredit", "supportsDebit"],
        supportedNetworks: ["amex", "discover", "masterCard", "visa"],
        countryCode: "US",

Safari only supports the Apple Pay payment method, but other browsers might support additional payment methods. When you specify multiple payment methods in a request, the browser decides which to present to your customer based on device availability and user preference.

Payment Details

Payment details are represented by the PaymentDetailsInit dictionary. It contains your transaction’s total amount, display items, shipping options, and payment method-specific modifiers (more on modifiers below). Here’s what valid payment details might look like for a $20 item plus tax and two shipping options:

const paymentDetails = {
    total: {
        label: "My Merchant",
        amount: { value: "27.50", currency: "USD" },
    displayItems: [{
        label: "Tax",
        amount: { value: "2.50", currency: "USD" },
    }, {
        label: "Ground Shipping",
        amount: { value: "5.00", currency: "USD" },
    shippingOptions: [{
        id: "ground",
        label: "Ground Shipping",
        amount: { value: "5.00", currency: "USD" },
        selected: true,
    }, {
        id: "express",
        label: "Express Shipping",
        amount: { value: "10.00", currency: "USD" },

You can choose a default shipping option by setting the selected attribute to true as we did above for "Ground Shipping". The total amount must not be negative, and when using Apple Pay, all payment amounts in your request must use the same ISO 4217 currency code. It is up to you to ensure the correctness of your payment details; Safari does not do any currency calculations on your behalf.

What about modifiers?

You can optionally include a sequence of modifiers in your payment details. Modifiers update your transaction’s display items and total when criteria you specify for a given payment method are satisfied. In Apple Pay, you can use modifiers to adjust the price based on the type of payment card selected in the Apple Pay payment sheet. For instance, the following modifier applies a $1.00 discount when your customer selects a debit card in Apple Pay:

const debitModifier = {
    supportedMethods: "",
    data: { paymentMethodType: "debit" },
    total: {
        label: "My Merchant",
        amount: { value: "26.50", currency: "USD" },
    additionalDisplayItems: [{
        label: "Debit Card Discount",
        amount: { value: "-1.00", currency: "USD" },

Modifiers provide some of the functionality present in the paymentmethodselected event from Apple Pay JS. See ApplePayModifier for more information.

Payment Options

Payment options are represented by the PaymentOptions dictionary. If you need to request your customer’s name, email address, or phone number – or request a certain type of shipping – you can do so here:

const paymentOptions = {
    requestPayerName: true,
    requestPayerEmail: true,
    requestPayerPhone: true,
    requestShipping: true,
    shippingType: "shipping",

If you set requestShipping to true, the shipping options you specified in Payment Details are presented in the payment sheet for your customer to choose between. You receive the requested information once your customer authorizes payment.


Safari might raise an exception when constructing a new PaymentRequest. Exceptions can occur for the following reasons:

  • The frame is not in a secure context.
  • The frame is a cross-origin subframe.
  • No payment methods were specified.
  • A payment method identifier is invalid.
  • Calling JSON.stringify() on the payment method data failed.
  • Invalid currency amounts were specified (e.g., negative total or multiple currencies).

canMakePayment() method

Once you’ve constructed a PaymentRequest, you can ask it if your customer will be able to authorize a transaction given the payment methods you can accept. You do this by calling the canMakePayment() method, which returns a promise that resolves to either true or false. In Safari, when Apple Pay is one of the payment methods, canMakePayment() resolves to true only if your customer has an active card enrolled in Apple Pay. This is the equivalent of how ApplePaySession.canMakePaymentsWithActiveCard() behaves in Apple Pay JS.

As we discussed in Showing Apple Pay Buttons, the Apple Pay Human Interface Guidelines require you to show an Apple Pay button whenever your customer is on supported hardware, whether or not they have an active card enrolled. Therefore, you should not hide Apple Pay buttons when canMakePayment() resolves to false. Always show an Apple Pay button if ApplePaySession.canMakePayments() returns true, and always present the Apple Pay payment sheet when your customer taps or clicks the button. Safari prompts your customer to enroll a payment card if they haven’t done so already before continuing with your transaction. For more information, see Human Interface Guidelines > Apple Pay on the Web.

show() method

When your customer taps or clicks an Apple Pay button, you should present the Apple Pay payment sheet. You do this by calling the show() method, which returns a promise that resolves to a PaymentResponse once your customer authorizes payment. The promise is rejected with an AbortError if your customer cancels the transaction.

You can optionally call show() with a promise for a PaymentDetailsUpdate. Sometimes you might still be in the process of calculating payment details when your customer taps or clicks the Apple Pay button. In this case, you can construct a new PaymentRequest with placeholders for details, then call show() with a promise to provide up-to-date details later. When you resolve this promise, Safari displays the updated details in the Apple Pay payment sheet.

Safari might reject the promise returned by show() with an exception. Exceptions can occur for the following reasons:

  • show() was not triggered by user activation (e.g., a tap or click).
  • The request has already been aborted.
  • An Apple Pay session is already active.
  • Payment method data is invalid (e.g., is missing required fields).

abort() method

If you need to abort the presented transaction, you can call the abort() method. When you do this, Safari dismisses the Apple Pay payment sheet and rejects the promise returned by show() with an AbortError. If the transaction has already been aborted, or show() has not yet been called, calling abort() throws an InvalidStateError.

Merchant Validation

Before Safari can present the Apple Pay payment sheet, you must acquire a payment session from Apple. This process is referred to as merchant validation.

Soon after you call show(), Safari dispatches the merchantvalidation event to your PaymentRequest object. The event defines a validationURL attribute representing the Apple URL your server contacts to receive a payment session. You must call the event’s complete() method with a promise that you resolve with this payment session once you receive it.

Here is what a merchantvalidation event handler might look like:

request.onmerchantvalidation = function (event) {
    const sessionPromise = fetchPaymentSession(event.validationURL);

You can learn more about merchant validation from Requesting an Apple Pay Payment Session.

Shipping Events

Once you’ve received a merchant session, Safari presents the Apple Pay payment sheet to your customer. If you’ve requested shipping, your customer is able to select between your shipping options and provide a shipping address. When they make these selections in the payment sheet, Safari dispatches a shippingoptionchange or shippingaddresschange event to your PaymentRequest object.


When the user selects a shipping option, Safari dispatches the shippingoptionchange event. In your event handler, you can determine the selected shipping option by checking the PaymentRequest‘s shippingOption attribute. To update the payment details based on the selected shipping option, call updateWith() on the event object with a promise that resolves to a PaymentDetailsUpdate.

When requesting shipping with Apple Pay, you must always listen for shippingoptionchange and call updateWith() with a promise that resolves within 30 seconds, otherwise, the transaction will time out.


When your customer selects a shipping address, Safari dispatches the shippingaddresschange event. In your event handler, you can determine the selected shipping address by checking the PaymentRequest‘s shippingAddress attribute. To update the payment details based on the selected shipping address, call updateWith() on the event object with a promise that resolves to a PaymentDetailsUpdate. If you are unable to ship to the selected address, you can provide an error message in your PaymentDetailsUpdate that Safari displays to your customer.

When using Apple Pay, Safari might redact some details from the shipping address. For instance, in the United States, only city, state, 5-digit ZIP code, and country are provided. Safari provides the full, un-redacted shipping address once your customer authorizes payment.

When requesting shipping with Apple Pay, you must always listen for shippingaddresschange and call updateWith() with a promise that resolves within 30 seconds, otherwise the transaction will time out.

Handling Payment Authorization

When your customer authorizes payment, Safari resolves the promise you received from calling show() with a PaymentResponse. Depending on what you requested in your PaymentOptions, the response might contain the selected shipping option, shipping address, name, email, and phone number of your customer.

The response also contains the payment method identifier used to conduct the transaction (methodName), along with its associated details. When Apple Pay is the selected payment method, the associated details is an ApplePayPayment dictionary. ApplePayPayment contains the Apple Pay token you use to process the payment authorization. It also includes your customer’s billing and shipping contact information as ApplePayPaymentContacts if you required this in your ApplePayRequest.

When you have finished processing the payment authorization, you call the complete() method on PaymentResponse to indicate the result of your processing. You can call complete() with a status of "success" or "failure". At this point, the Apple Pay payment sheet is dismissed.


You now have all the pieces you need to conduct an Apple Pay transaction using Payment Request. Here’s what an Apple Pay session might look like using Payment Request:

async function applePayButtonClicked()
    // Consider falling back to Apple Pay JS if Payment Request is not available.
    if (!window.PaymentRequest)

    try {
        const request = new PaymentRequest([applePayMethod], paymentDetails, paymentOptions);

        request.onmerchantvalidation = function (event) {
            // Have your server fetch a payment session from event.validationURL.
            const sessionPromise = fetchPaymentSession(event.validationURL);

        request.onshippingoptionchange = function (event) {
            // Compute new payment details based on the selected shipping option.
            const detailsUpdatePromise = computeDetails();

        request.onshippingaddresschange = function (event) {
            // Compute new payment details based on the selected shipping address.
            const detailsUpdatePromise = computeDetails();

        const response = await;
        const status = processResponse(response);
    } catch (e) {
        // Handle errors

Let’s see how this works in a live demo. If you are viewing this post on a device capable of Apple Pay, you should see an Apple Pay button below. Feel free to click it! Don’t worry, no matter what you do in the payment sheet, your card won’t be charged anything.


The Payment Request API is available in Safari 11.1 on macOS Sierra and macOS High Sierra, Safari on iOS 11.3, and Safari Technology Preview.

More Information

Apple provides comprehensive documentation for Apple Pay on the Web. Here are a few links you might find useful:


We’d love to hear your feedback! If you find a Payment Request bug, please report it at On Twitter, you can reach the WebKit team at @webkit, or our web technologies evangelist Jonathan Davis at @jonathandavis.

April 05, 2018 05:00 PM

April 04, 2018

Release Notes for Safari Technology Preview 53

Surfin’ Safari

Safari Technology Preview Release 53 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 229535-230029.

This release of Safari Technology Preview has a known issue where the modal won’t appear for websites that prompt for camera or microphone access.

Service Workers

  • Changed to use one service worker process per security origin (r229735)
  • Changed to use the same SWServer for all ephemeral sessions (r229872)
  • Fixed promptly terminating service worker processes when they are no longer needed (r229927)
  • Included the security origin in the service worker process name (r229878)


  • Added support for VCP encoder on macOS and iOS (r229920)
  • Fixed the RTCPeerConnection constructor to throw an exception for bad configuration parameters (r229645)
  • Fixed setting SenderTrack to null calling removeTrack with RTCRtpSender (r229587)


  • Fixed CSS mask images to be retrieved using potentially CORS-enabled fetch (r230006)
  • Fixed loading the stylesheet when changing the <link> element rel attribute from preload to stylesheet (r229585)


  • Fixed invalidating descendants for :nth-child and :nth-of-type pseudo classes only when needed (r229537)
  • Fixed positioning for text with letter spacing (r229867)


  • Added Fullscreen API as an Experimental Feature (r229680)
  • Prevented SVG root from being skipped while marking percentage height descendants dirty (r229849)


  • Fixed table row count when role="row" is added to in DOM (r229879)


  • Fixed CSS Grid auto repeat tracks computation with definite min sizes (r229897)


  • Added a query and fragment exception to the History API’s unique origin restriction (r229540)

Web Inspector

  • Changed “Force Print Media Styles” to not persist across Web Inspector sessions (r229686)
  • Changed to not show checkboxes for invalid properties in the Styles sidebar (r229941)
  • Fixed the ability to add a new class by editing the class attribute in the DOM tree outline (r229744)
  • Fixed an instance of the main WebGL canvas having no reported size in the Canvas Tab (r229659)
  • Fixed a recording initiated by the user to properly show immediately on completion (r229620)
  • Fixed session dividers not being added when Console tab is not visible (r229785)
  • Fixed flashing when switching between nodes in the Styles sidebar (r229922)
  • Fixed losing focus when editing a property while a page is being loaded (r229787)
  • Prevented the Shift-Command-Left Arrow (⇧⌘←) and Shift-Command-Right Arrow (⇧⌘→) keys from switching tabs when focused on color picker text fields (r230001)
  • Removed redundant tooltips (r229543)

April 04, 2018 05:00 PM

April 03, 2018

Manuel Rego: Getting rid of "grid-" prefix on CSS Grid Layout gutter properties

Igalia WebKit

Early this year I was working on unprefixing the CSS Grid Layout gutter properties. The properties were originally named grid-column-gap and grid-row-gap, together with the grid-gap shorthand. The CSS Working Group (CSSWG) decided to remove the grid- prefix from these properties last summer, so they could be extended to be used in other layout models like Flexbox.

I was not planning to write a blog post about this, but the task ended up becoming something more than just renaming the properties, so this post describes what it took to implement this. Also people got quite excited about the possibility of animating grid gutters when I announced that this was ready on Twitter.

The task

So the theory seems pretty simply, we currently have 3 properties with the grid- prefix and we want to remove it:

  • grid-column-gap becomes column-gap,
  • grid-row-gap becomes row-gap and
  • grid-gap becomes gap.

But column-gap is already an existent property, defined by the Multicolumn spec, which has been around for a long time. So we cannot just create a new property, but we have to make it work also for Grid Layout, and be sure that the syntax is equivalent.

Animatable properties

When I started to test Multicol column-gap I realized it was animatable, however our implementations (Blink and WebKit) of the Grid Layout gutter properties were not. We’d need to make our properties animatable if we want to remove the prefixes.

More on that, I found a bug on Multicol column-gap animation, as its default computed value is normal, and it shouldn’t be possible to animate it. This was fixed quickly by Morten Stenshorne from Google.

Making the properties animatable is not complex at all, both Blink and WebKit have everything ready to make this task easy for properties like the gutter ones that represent lengths. So I decided to do this as part of the unprefixing patch, instead of something separated.

CSS Grid Layout gutters animation example (check it live)


But there was something else, the Grid gutter properties accept percentage values, however column-gap hadn’t that support yet. So I added percentage support to column-gap for multicolumn, as a preliminary patch for the unprefixing one.

There has been long discussions in the CSSWG about how to resolve percentages on gutter properties. The spec has recently changed so these properties should be resolved to zero for content-based containers. However my patch is not implementing that, as we don’t believe there’s an easy way to support something like that in most of the web engines, and Blink and WebKit are not exceptions. Our patch follows what Microsoft Edge does in these cases, and resolves the percentage gaps like it does for percentage widths or heights. And the Firefox implementation that has just landed this week does the same.

CSS Multi-column percentage column-gap example (check it live)

I guess we’ll still have some extra discussions about this topic in the CSSWG, but percentages themselves deserve their own blog post.


Once all the previous problems got solved, I landed the patches related to unprefixing the gutter properties in both Blink and WebKit. So you can use the unprefixed version since Chrome 66.0.3341.0 and Safari Technology Preview 50.

<div style="display: grid; grid: 100px 50px / 300px 200px;
            column-gap: 25px; row-gap: 10px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
  <div>Item 4</div>

A simple Grid Layout example using the unprefixed gutter properties A simple Grid Layout example using the unprefixed gutter properties

Note that as specified in the spec, the previous prefixed properties are still valid and will be kept as an alias to avoid breaking existent content.

Also it’s important to notice that now the gap shorthand applies to Multicol containers too, as it sets the value of column-gap longhand (together with row-gap which would be ignored by Multicol).

<div style="column-count: 2; gap: 100px;">
  <div>First column</div>
  <div>Second column</div>

Multicolumn example using gap property Multicolumn example using gap property

Web Platform Tests

As usual in our last developments, we have been using web-platform-tests repository for all the tests related to this work. As a result of this work we have now 16 new tests that verify the support of these properties, including tests for animations stuff too.

Running those tests on the different browsers, I realized there was an inconsistency between css-align and css-multicol specifications. Both specs define the column-gap property, but the computed value was different. I raised a CSSWG issue that has been recently solved, so that the computed value for column-gap: normal should still be normal. This causes that the property won’t be animatable from normal to other values as explained before.

This is the summary of the status of these tests in the main browser engines:

  • Blink and WebKit: They pass all the tests and follow last CSSWG resolution.
  • Edge: Unprefixed properties are available since version 41. Percentage support is interoperable with Blink and WebKit. The computed value of column-gap: normal is not normal there, so this needs to get updated.
  • Firefox: It doesn’t have support for the unprefixed properties yet, however the default computed value is normal like in Blink and WebKit. But Multicol column-gap percentage support has just been added. Note that there are already patches on review for this issue, so hopefully they’ll be merged in the coming days.


The task is completed and everything should be settled down at this point, you can start using these unprefixed properties, and it seems that Firefox will join the rest of browser by adding this support very soon.

Igalia and Bloomberg working together to build a better web Igalia and Bloomberg working together to build a better web

Last, but not least, this is again part of the ongoing collaboration between Igalia and Bloomberg. I don’t mind to repeat myself over and over, but it’s really worth to highlight the support from Bloomberg in the CSS Grid Layout development, they have been showing to the world that an external company can directly influence in the new specifications from the standard bodies and implementations by the browser vendors. Thank you very much!

Finally and just as a heads-up, I’ll be in Berlin next week for the CSSWG F2F meeting. I’m sure we’ll have interesting conversations about CSS Grid Layout and many other topics there.

April 03, 2018 10:00 PM

March 22, 2018

Clipboard API Improvements

Surfin’ Safari

The Clipboard API provides a mechanism for websites to support accessing the system pasteboard (pasteboard is the macOS and iOS counterpart to clipboard on Windows and Linux). Copy and paste is one of the most basic interactions in modern operating systems. We use it for all sorts of purposes, from copying a hyperlink on one website to another, to copying a blog post typed in a native word processing application to a blog platform on the web. For this reason, creating a compelling productivity application such as a word processor and a presentation application on the Web requires interacting with the system pasteboard just as much as other native applications.

Over the last couple of months, we have added support for new API for better interoperability with other browsers, and refined our implementations to allow more use cases in macOS and iOS ports of WebKit. These changes are available for you review in Safari 11.1 and iOS 11.3 beta programs.

First, we modernized our DataTransfer API. We added support for items, and fixed many bugs on macOS and iOS. Because most websites don’t support uploading TIFF files, WebKit now automatically converts TIFF images to PNG images and exposes PNG images as files when there are images in the system pasteboard.

Directory Upload

In r221177, we added support for uploading directories via DataTransfer.webkitGetAsEntry() and input.webkitdirectory to be interoperable with other browsers such as Chrome, Firefox, and Edge which had already implemented this WebKit-prefixed feature. This new API allows users to upload a whole directory onto Cloud storage and file sharing services such as iCloud and Dropbox. On iOS, directory upload is supported when dragging folders from the Files app and dropping into web pages.

Custom MIME Types

Because the system pasteboard is used by other native applications, there are serious security and privacy implications when exposing data to web content through the clipboard API. If a website could insert arbitrary content into the system pasteboard, the website can exploit security bugs in any native application which reads the pasteboard content — for instance, a utility application which shows the content put into the pasteboard. Similarly, if a website could read the system pasteboard at any given point in time, it can potentially steal sensitive information such as user’s real full name and mailing addresses that the user was copying.

For this reason, we previously didn’t allow reading of anything but plain text and URL in DataTransfer objects. We relaxed this restriction in r222595 by allowing reading and writing of arbitrary MIME types between web pages of the same origin. This change allows web applications from a single origin to seamlessly share information using their own MIME types and MIME types we don’t support, while still hiding privacy and security sensitive information other native applications may put into the system pasteboard. Because custom MIME types used by websites are bundled together under a special MIME type that WebKit controls, web pages can’t place malicious payloads of arbitrary MIME types in the system pasteboard to exploit bugs in native applications.

Getting and Setting Data

Apart from custom MIME types, web applications may now write text/html, text/plain and text/uri-list to the system pasteboard using DataTransfer.setData or DataTransfer.items.add during a copy or dragstart event. This content is written with the appropriate UTI for macOS and iOS, so pasting into native applications that are already capable of pasting HTML markup, plain text strings, or URLs will work as expected.

On the reading side, web applications may now also use DataTransfer.getData and DataTransfer.items during a paste and drop event to read text/html, text/plain and text/uri-list data from the system pasteboard. If any files were written to the pasteboard — for example, when copying a PDF file in Finder — this information will be accessible through DataTransfer.files and DataTransfer.items; for backwards compatibility, the “Files” type will also be added to the list of types in DataTransfer.types to indicate that file data may be requested by the page.

An important caveat is that native applications may write file paths to the pasteboard as URLs or plain text while copying files. This may cause users to unknowingly expose file paths to the home directory and private containers of native applications. Thus, WebKit implements heuristics to suppress access to this data via DataTransfer API in such cases. If the pasteboard contains at least one file and text/uri-list is requested, the scheme of the URL must be http, https, data, or blob in order for WebKit to expose it to the page. Other schemes, such as file or ftp, will result in an empty string. Likewise, requests for text/plain will return the empty string when there are files on the pasteboard.

Reading and Writing HTML Content

Among other MIME types, HTML content is most pervasive on the web. Unfortunately, letting arbitrary websites write HTML content into the system pasteboard is problematic because HTML can contain script tags and event handlers which can end up executing malicious scripts in the application reading the content. Letting websites read arbitrary HTML content in the system pasteboard is also problematic because some word processor and spreadsheet applications put privacy sensitive information such as local file paths and user information into the HTML placed in the system pasteboard. For example, if an user typed 12345 into an unsaved spreadsheet, and copied & pasted into a random website, the website might be able to learn user’s local home directory path if we were to expose the raw HTML content placed in the pasteboard by other native applications. For this reason, we previously didn’t allow reading or writing of HTML content via DataTransfer objects. Instead, websites had to wait for WebKit’s native editing code to paste the content and process it afterwards.

In r223440, we introduced a mechanism to sanitize HTML read from and written to the system pasteboard, allowing us to lift this restriction. When the website tries to write HTML to the pasteboard, we paste the HTML into a dummy document, re-serialize it to HTML, and then write the re-serialized HTML into the system pasteboard. This process ensures any script elements, event handlers, and other potentially dangerous content will be stripped away. We also package all the necessary sub-resources in the HTML such as images into WebArchive so that native applications which reads the pasteboard content doesn’t have to re-fetch those resources upon paste. Similarly, when a website tries to read the HTML content placed by other native applications, we run through the same steps of pasting the content into a dummy document and re-serializing HTML, stripping away any private information the user didn’t intend to include in the pasted content. Sanitization also happens when HTML content is copied and pasted across different origins but not within web pages of the same origin. As a result, websites can write arbitrary HTML contents via clipboard API and read the exact same content back later within a single origin.

Pasting HTML Content with Images

We also made a major change in the way we handle local files included in the pasted HTML content. Previously, sub-resources (such as image files in pasted content) used URLs of the form webkit-fake-url://<filename> where <filename> is the filename of the sub-resource. Because this is not a standard protocol the website can access, the pasted images’ data were inaccessible to websites. Even though WebKit is capable of loading these images, there was no way for websites to save the images either to their service or into browser’s storage API. r223440 replaces these fake URLs with blob URLs so that the website can save the images. We also use blob URLs instead of fake URLs when pasting RTFD content since r222839.

This change provides a mechanism for Web applications to save images included in pasted content using the Blob API. For example, an online e-mail editor now has the capability to save images that a user copied and pasted from TextEdit or Microsoft Word on iOS and macOS. We’re pleased to be the first browser to provide this powerful platform integration capability to Web developers.


We’re excited to empower productivity apps on the Web to more seamlessly integrate with native applications on macOS and iOS via the updated clipboard API. We’d also like to give special thanks to the developers of TinyMCE who have tirelessly worked with us to resolve many bugs involving copy and paste from Microsoft Word to high profile websites which use TinyMCE.

March 22, 2018 05:00 PM

March 21, 2018

Release Notes for Safari Technology Preview 52

Surfin’ Safari

Safari Technology Preview Release 52 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 228856-229535.

Legacy NPAPI Plug-ins

  • Removed support for running legacy NPAPI plug-ins other than Adobe Flash

Service Worker

  • Changed Fetch event release assert to take into account the fetch mode (r228930)
  • Changed to not use a Service Worker in the case of document redirection if it will be already served by AppCache (r229086)
  • Fix loads for a Document controlled by a Service Worker to not use AppCache (r229181)
  • Updated Service Worker to respect IndexedDB and DOM cache partitioning (r229483)


  • Added support for preconnect link headers (r229308)
  • Fixed converting a load to a download to work with async policy delegates (r229177)
  • Prevented DNS prefetching from being re-enabled (r229061)


  • Fixed handling undefined global variables with the same name as an element ID (r229451)
  • Made Number.isInteger an intrinsic (r228968)


  • Added new CSS env() constants for use with fullscreen (r229475)
  • Fixed ::selection CSS stroke-color and stroke-width to be applied to selected text in text fields (r229147)


  • Fixed HTML pattern attribute to set u flag for regular expressions (r229363)
  • Fixed replaceState causing back and forward navigation problems on a page with <base href="/"> (r229375)
  • Fixed to cancel navigation policy check in addition to cancelling the existing provisional load (r228922)


  • Added more accessibility events support (r229310)
  • Dispatched accessiblesetvalue event (r229112)
  • Fixed keyboard focus to follow the VoiceOver cursor into web content or within web content (r228857)
  • Fixed WebKit running spell checker even on non-editable content text (r229500)

Web Driver

  • Fixed clicking on a disabled option element to not produce an error (r229212)
  • Fixed stale elements not getting detected when removed from the DOM (r229210)
  • Fixed failed provisional loads causing “Navigate To” command to hang (r228887)
  • Fixed script evaluations via WebDriver to have a user gesture indicator (r229206)

Web Inspector

  • Changed Canvas Tab to scroll into view and inspect an element if Canvas has a DOM node (r229044)


  • Added cache for memory address and size on an instance (r228966)


  • Fixed the webkitfullscreenchange event to fire at the same time as :-webkit-full-screen pseudo selector changes (r229466, r229487)

Bug Fix

  • Fixed copying a table from the Numbers app and pasting into iCloud Numbers (r229503)

March 21, 2018 05:00 PM

March 18, 2018

Philippe Normand: Web Engines Hackfest 2014

Igalia WebKit

Last week I attended the Web Engines Hackfest. The event was sponsored by Igalia (also hosting the event), Adobe and Collabora.

As usual I spent most of the time working on the WebKitGTK+ GStreamer backend and Sebastian Dröge kindly joined and helped out quite a bit, make sure to read …

By Philippe Normand at March 18, 2018 09:18 AM

March 16, 2018

Protecting Against HSTS Abuse

Surfin’ Safari

HTTP Strict Transport Security (HSTS) is a security standard that provides a mechanism for web sites to declare themselves accessible only via secure connections, and to tell web browsers where to go to get that secure version. Web browsers that honor the HSTS standard also prevent users from ignoring server certificate errors.

Apple uses HSTS on, for example, so that any time a visitor attempts to navigate to the insecure address “” either by typing that web address, or clicking on a link, they will be automatically redirected to “”. HSTS will also cause the web browser to go to the secure site in the future, even if the insecure address is used. This is a great feature that prevents a simple error from placing users in a dangerous state, such as performing financial transactions over an unauthenticated connection.

What could be wrong with that?

Well, the HSTS standard describes that web browsers should remember when redirected to a secure location, and to automatically make that conversion on behalf of the user if they attempt an insecure connection in the future. This creates information that can be stored on the user’s device and referenced later. And this can be used to create a “super cookie” that can be read by cross-site trackers.

HSTS as a Persistent Cross-Site Identifier (aka “Super Cookie”)

An attacker seeking to track site visitors can take advantage of the user’s HSTS cache to store one bit of information on that user’s device. For example, “load this domain with HTTPS” could represent a 1, while no entry in the HSTS cache would represent a 0. By registering some large number of domains (e.g., 32 or more), and forcing resource loads from a controlled subset of those domains, they can create a large enough vector of bits to uniquely represent each site visitor.

The HSTS authors recognized this possibility in Section 14.9 of their spec:

…it is possible for those who control one or more HSTS Hosts to encode information into domain names they control and cause such UAs to cache this information as a matter of course in the process of noting the HSTS Host. This information can be retrieved by other hosts through cleverly constructed and loaded web resources, causing the UA to send queries to (variations of) the encoded domain names.

On the initial website visit:

  • A random number is assigned to the visitor, for example 8396804.
  • This can be represented as a binary value (e.g., 100000000010000000000100)
  • The tracker script then makes subresource requests to a tracker-controlled domain over https, one request per active bit in the tracking identifier.
    • … and so on.
  • The server responds to each HTTPS request with an HSTS response header, which caches the tracking value in the web browser.
  • Now we are guaranteed to load the HTTPS version of,, and, even if the load is attempted over HTTP.

On subsequent website visits:

  • The tracker script loads 32 invisible pixels over HTTP that represent the bits in the binary number.
  • Since some of those bits (,, and in our example) were loaded with HSTS, they will automatically be redirected to HTTPS.
  • The tracking server transmits one image when they are requested over HTTP, and a different image when requested over HTTPS.
  • The tracking script recognizes the different images, turns those into zero (HTTP) and one (HTTPS) bits in the number, and voila — your unique binary value is recreated and you are tracked!

Attempts to mitigate this attack are challenging because of the difficulty in balancing security and privacy goals. Improperly mitigating the attack also runs the risk of weakening important security protections.


Periodically, the privacy risks of HSTS are discussed in the media as a theoretical tracking vector (e.g., [1], [2], and [3]). Absent evidence of actual malicious abuse of the HSTS protocol, browser implementors erred on the side of caution and honored all HSTS instructions provided by sites.

Recently we became aware that this theoretical attack was beginning to be deployed against Safari users. We therefore developed a balanced solution that protects secure web traffic while mitigating tracking.

Apple’s Solution

The HSTS exploit consists of two phases: the initial tracking identifier creation phase, and the subsequent read operation. We decided to apply mitigations to both sides of the attack.

Mitigation 1: Limit HSTS State to the Hostname, or the Top Level Domain + 1

We observed tracking sites constructing long URL’s encoding the digits in various levels of the domain name.

For example:

We also observed tracking sites using large number of sibling domain names, for example:

Telemetry showed that attackers would set HSTS across a wide range of sub-domains at once. Because using HSTS in this way does not benefit legitimate use cases, but does facilitate tracking, we revised our network stack to only permit HSTS state to be set for the loaded hostname (e.g., “”), or the Top Level Domain + 1 (TLD+1) (e.g., “”).

This prevents trackers from efficiently setting HSTS across large numbers of different bits; instead, they must individually visit each domain representing an active bit in the tracking identifier. While content providers and advertisers may judge that the latency introduced by a single redirect through one origin to set many bits is imperceptible to a user, requiring redirects to 32 or more domains to set the bits of the identifier would be perceptible to the user and thus unacceptable to them and content providers. WebKit also caps the number of redirects that can be chained together, which places an upper bound on the number of bits that can be set, even if the latency was judged to be acceptable.

This resolves the setting side of the super cookie equation.

Mitigation 2: Ignore HSTS State for Subresource Requests to Blocked Domains

We modified WebKit so that when an insecure third-party subresource load from a domain for which we block cookies (such as an invisible tracking pixel) had been upgraded to an authenticated connection because of dynamic HSTS, we ignore the HSTS upgrade request and just use the original URL. This causes HSTS super cookies to become a bit string consisting only of zeroes.


Telemetry gathered during internal regression testing, our public seeds, and the final public software release indicates that the two mitigations described above successfully prevented the creation and reading of HSTS super cookies while not regressing the security goals of first party content. We believe them to be consistent with best practices, and to maintain the important security protections provided by HSTS. We have shared the details of Mitigation 1 with the authors of RFC 6797, and are working to incorporate the behavior as part of the standard.

However, the internet is a wide space full of unique and amazing uses of Web Technology. If you feel that you have a legitimate case where these new rules are not working as intended, we would like to know about it. Please send feedback and questions to or @webkit on Twitter, and file any bugs that you run into on WebKit’s bug tracker.



March 16, 2018 06:00 PM

March 14, 2018

Intelligent Tracking Prevention 1.1

Surfin’ Safari

In June of last year, we announced Intelligent Tracking Prevention, or ITP. ITP is a privacy feature which detects domains that have the ability to track the user cross-site and either partitions or purges the associated website data.

The biggest update to ITP so far is the introduction of the Storage Access API which provides a mechanism for embedded third-party content to get out of cookie partitioning through user interaction. In addition to the Storage Access API, ITP 1.1 includes two behavior changes described below.

Partitioned Cookies No Longer Persisted to Disk

With ITP 1.1, all partitioned cookies are treated as session cookies and are not persisted to disk.

Domains that have their cookies partitioned by ITP have a way to get access to their non-partitioned cookies through the Storage Access API. Therefore there is no longer a need to persist partitioned cookies across browsing sessions.

Cookies Blocked If They Will Be Purged Anyway

ITP’s purging of cookies and other website data happens once an hour for performance reasons. In between purges, ITP 1.0 would partition cookies for domains with a pending purge to make sure there were no gaps where cross-site tracking could happen. This caused a situation where cookies were purged shortly after being created, potentially confusing servers.

With ITP 1.1, domains with a pending purge will not be able to set new cookies and their existing cookies are not sent in requests. This makes the transition from partitioned cookies to purged cookies distinct and easier to handle for developers.

Intelligent Tracking Prevention 1.1 Timeline


These updates to Intelligent Tracking Prevention are available in Safari 11.1 on iOS 11.3 beta and macOS High Sierra 10.13.4 beta, as well as in Safari Technology Preview. Please report bugs through, or send feedback on Twitter to the team @webkit, or our evangelist @jonathandavis. If you have technical questions about these changes, you can find me on Twitter @johnwilander.

March 14, 2018 08:00 PM

March 07, 2018

Release Notes for Safari Technology Preview 51

Surfin’ Safari

Safari Technology Preview Release 51 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 228454-228856.

This release of Safari Technology Preview may reset your homepage and search engine preferences to Safari’s defaults.


  • Added accessibleclick event (r228827)


  • Disallowed cross-origin subresources from asking for credentials (r228486)
  • Prevented blocking authentication challenges to navigated resources (r228703)


  • Fixed provisional loads that might get committed before receiving the decidePolicyForNavigationResponse response (r228852)

Service Workers

  • Fixed the ability to download resources loaded from Service Workers (r228551)


  • Changed to handle all SVG writing modes (r228822)


  • Improved the speed of descendent selector invalidation by using a selector filter (r228729)

Web Inspector

  • Added support to show or hide the navigation sidebar panel based on the current view (r228722)
  • Fixed hiding the completion popover when switching panels in the Styles sidebar (r228487)


  • Added support for scrolling a non-editable web-selection and start autoscroll when near screen edges (r228549)

March 07, 2018 06:00 PM

February 21, 2018

Introducing Storage Access API

Surfin’ Safari

In June last year we introduced Intelligent Tracking Prevention (ITP). ITP is a privacy feature that detects which domains have the ability to track the user cross-site and either partitions the domain’s cookies or purges its website data all together.

The strongest developer feedback we got on ITP was that it needs to provide a way for embedded cross-site content to authenticate users who are already logged in to their first-party services. Today we are happy to provide a solution in the form of Storage Access API. It allows for authenticated embeds while continuing to protect customers’ privacy by default.

Partitioned Cookies and Embedded Content

Let’s say that is embedded on multiple websites to facilitate commenting or “liking” content with the user’s socialexample ID. ITP will detect that such multi-page embeds gives the ability to track the user cross-site and therefore deny embedded content from access to its first-party cookies, providing only partitioned cookies. This breaks the user’s ability to comment and like content unless they have interacted with as first-party site in the last 24 hours. (Please see the original ITP blog post for the exact rules around partitioned cookies.)

The same goes for embedded third-party payment providers and embedded third-party videos from subscription services. As soon as ITP detects their tracking abilities, it denies them first-party cookie access outside the 24 hour window, and the embedded content treats the user as logged out even though they are logged in.

We’ve made tradeoffs for user privacy. But it would be even better if we could provide the benefits of being logged in to third party iframes, provided that the user is actually interested in using them, while still protecting privacy.

The Solution: Storage Access API

The solution is to allow third-party embeds to request access to their first-party cookies when the user interacts with them. To do this, we created the Storage Access API.

The Storage Access API offers two new functions to cross-origin iframes — document.hasStorageAccess() and document.requestStorageAccess(). It also offers the embedding top frame a new iframe sandbox token — “allow-storage-access-by-user-activation”.

Storage access in this context means that the iframe has access to its first-party cookies, i.e. the same cookies it would have access to as a first-party site. Note that storage access does not relax the same-origin policy in any way. Specifically, this is not about third-party iframes getting access to the embedding website’s cookies and storage, or vice versa.

WebKit’s implementation of the API only covers cookies for now. It does not affect the partitioning of other storage forms such as IndexedDB or LocalStorage.

Check For Storage Access

A call to document.hasStorageAccess() returns a promise that resolves with a boolean indicating whether the document already has access to its first-party cookies or not. Should the iframe be same-origin as the top frame, the promise returns true.

var promise = document.hasStorageAccess();
  function (hasAccess) {
    // Boolean hasAccess says whether the document has access or not.
  function (reason) {
    // Promise was rejected for some reason.

Request Storage Access

A call to document.requestStorageAccess() upon a user gesture such as a tap or click returns a promise that is resolved if storage access was granted and is rejected if access was denied. If storage access was granted, a call to document.hasStorageAccess() will return true. The reason why iframes need to call this API explicitly is to offer developers control over when the document’s cookies change.

function makeRequestWithUserGesture() {
  var promise = document.requestStorageAccess();
    function () {
      // Storage access was granted.
    function () {
      // Storage access was denied.
<button onclick="makeRequestWithUserGesture()">Play video</button>

The iframe needs to adhere to a set of rules to be able to get storage access granted. The basic rules are:

  • The iframe’s cookies need to be currently partitioned by ITP. If they’re not, the iframe either already has cookie access or cannot be granted access because its cookies have been purged.
  • The iframe needs to be a direct child of the top frame.
  • The iframe needs to be processing a user gesture at the time of the API call.

Below are the detailed rules for the promise returned by a call to document.requestStorageAccess(). When we say eTLD+1 we mean effective top-level domain + 1. An eTLD is .com or so an example of an eTLD+1 would be but not (eTLD+2) or (just eTLD).

  1. If the sub frame is sandboxed but doesn’t have the tokens “allow-storage-access-by-user-activation” and “allow-same-origin”, reject.
  2. If the sub frame’s parent is not the top frame, reject.
  3. If the browser is not processing a user gesture, reject.
  4. If the sub frames eTLD+1 is equal to the top frame’s eTLD+1, resolve. As an example, has the same eTLD+1 as
  5. If the sub frame’s origin’s cookies are currently blocked, reject. This means that ITP has either purged the origin’s website data or will do so in the near future. Thus there is no storage to get access to.
  6. If all the above has passed, resolve.

Access Removal

Storage access is granted for the life of the document as long as the document’s frame is attached to the DOM. This means:

  • Access is removed when the sub frame navigates.
  • Access is removed when the sub frame is detached from the DOM.
  • Access is removed when the top frame navigates.
  • Access is removed when the webpage goes away, such as a tab close.

Sandboxed Iframes

If the embedding website has sandboxed the iframe, it cannot be granted storage access by default. The embedding website needs to add the sandbox token “allow-storage-access-by-user-activation” to allow successful storage access requests. The iframe sandbox also needs the tokens “allow-scripts” and “allow-same-origin” since otherwise it can’t call the API and doesn’t execute in an origin that can have cookies.

<iframe sandbox="allow-storage-access-by-user-activation allow-scripts allow-same-origin"></iframe>

A Note On Potential Abuse

We have decided not to prompt the user when an iframe calls the Storage Access API to make the user experience as smooth as possible. ITP’s rules are an effective gatekeeper for who can be granted access, and for the time being we rely on them.

However, we will monitor the adoption of the API and make changes if we find widespread abuse where the user is clearly not trying to take some authenticated action in the calling iframe. Such API behavior changes may be prompts, abuse detection resulting in a rejected promise, rate limiting of API calls per origin, and more.


Storage Access API is available in Safari 11.1 on iOS 11.3 beta and macOS High Sierra 10.13.4 beta, as well as in Safari Technology Preview 47+. If you’re interested in cross-browser compatibility, please follow the whatwg/html issue for Storage Access API.


Please report bugs through, or send feedback on Twitter to the team @webkit, or our evangelist @jonathandavis. If you have technical questions about how the Storage Access API works, you can find me on Twitter @johnwilander.

February 21, 2018 09:00 PM

Release Notes for Safari Technology Preview 50

Surfin’ Safari

Safari Technology Preview Release 50 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 227873-228454.

Service Workers

  • Added support for cache storage of blob responses (r228326)
  • Changed to queue a microtask when a waitUntil() promise is settled (r227959)
  • Delayed service worker process creation until actually needed (r227989)
  • Delayed saving service worker registrations to disk until after the activation succeeds (r228180)
  • Fixed issue with IndexedDB databases not persisting inside Service Workers (r228230)
  • Fixed issue where service workers jobs would sometimes not get processed anymore (r228101)
  • Fixed clearing a registration to properly null out its workers before setting their state to "redundant" (r228015)
  • Fixed clearing all service worker registrations to wait for importing the service worker registration to finish (r228025, r228034)
  • Started nulling out registration.installing before setting service worker state to “redundant” when install fails (r227997)

Web App Manifest

  • Changed to default Web App Manifest scope to the containing directory of the start URL when 'scope' is not specified (r228036)

Payment Request

  • Changed show() to take an optional PaymentDetailsUpdate promise (r228195)
  • Fixed payment sheet not dismissing when calling complete() with result "unknown" or "fail" (r228342)


  • Implemented createImageBitmap(HTMLVideoElement) (r228092)


  • Corrected invaliding style for sibling combinators on class change (r227956)
  • Fixed rendering SVG images with same size as WebGL texture (r228213)
  • Fixed computing inline-block baseline for vertical-lr (r227947)

Web Inspector

  • Added listing of Canvases, Programs, and Recordings to the sidebar (r228301)
  • Fixed the Canvas tab tree selection abruptly changing when selecting a recording frame (r228362)
  • Fixed pasting multiple properties to create properties instead of causing a bad property in the Styles Sidebar (r228030)
  • Fixed the completion popover not hiding when switching panels in the Styles Sidebar (r228232)
  • Fixed typing a value and quickly moving focus away sometimes displaying an outdated value in the Styles Sidebar (r228296)
  • Updated the Elements tab to have “Jump to Layer” functionality (r228215)

Web Driver

  • Changed cookies returned by automation to have expiry time in seconds (r227891)
  • Changed to not return an error if resizing or moving a window has no effect (r228434)
  • Prepended a dot to the domain when missing in the addCookie command (r228087, r228371)


  • Fixed Accessibility getting notified when a web process cancels suspension (r228350)
  • Deferred attribute computation until needed (r228279)
  • Deferred focus notifications for UI elements (r228417)


  • Changed to throw an exception when using structured cloning on a Symbol (r227969)
  • Fixed an incorrect case of variable resolution to consult the global lexical environment first before the global object (r227898)

February 21, 2018 06:00 PM

February 17, 2018

Michael Catanzaro: On Compiling WebKit (now twice as fast!)

Igalia WebKit

Are you tired of waiting for ages to build large C++ projects like WebKit? Slow headers are generally the problem. Your C++ source code file #includes a few headers, all those headers #include more, and those headers #include more, and more, and more, and since it’s C++ a bunch of these headers contain lots of complex templates to slow down things even more. Not fun.

It turns out that much of the time spent building large C++ projects is effectively spent parsing the same headers again and again, over, and over, and over, and over, and over….

There are three possible solutions to this problem:

  • Shred your CPU and buy a new one that’s twice as fast.
  • Use C++ modules: import instead of #include. This will soon become the best solution, but it’s not standardized yet. For WebKit’s purposes, we can’t use it until it works the same in MSVCC, Clang, and three-year-old versions of GCC. So it’ll be quite a while before we’re able to take advantage of modules.
  • Use unified builds (sometimes called unity builds).

WebKit has adopted unified builds. This work was done by Keith Miller, from Apple. Thanks, Keith! (If you’ve built WebKit before, you’ll probably want to say that again: thanks, Keith!)

For a release build of WebKitGTK+, on my desktop, our build times used to look like this:

real 62m49.535s
user 407m56.558s
sys 62m17.166s

That was taken using WebKitGTK+ 2.17.90; build times with any 2.18 release would be similar. Now, with trunk (or WebKitGTK+ 2.20, which will be very similar), our build times look like this:

real 33m36.435s
user 214m9.971s
sys 29m55.811s

Twice as fast.

The approach is pretty simple: instead of telling the compiler to build the original C++ source code files that developers see, we instead tell the compiler to build unified source files that look like this:

// UnifiedSource1.cpp
#include "CSSValueKeywords.cpp"
#include "ColorData.cpp"
#include "HTMLElementFactory.cpp"
#include "HTMLEntityTable.cpp"
#include "JSANGLEInstancedArrays.cpp"
#include "JSAbortController.cpp"
#include "JSAbortSignal.cpp"
#include "JSAbstractWorker.cpp"

Since files are included only once per translation unit, we now have to parse the same headers only once for each unified source file, rather than for each individual original source file, and we get a dramatic build speedup. It’s pretty terrible, yet extremely effective.

Now, how many original C++ files should you #include in each unified source file? To get the fastest clean build time, you would want to #include all of your C++ source files in one, that way the compiler sees each header only once. (Meson can do this for you automatically!) But that causes two problems. First, you have to make sure none of the files throughout your entire codebase use conflicting variable names, since the static keyword and anonymous namespaces no longer work to restrict your definitions to a single file. That’s impractical in a large project like WebKit. Second, because there’s now only one file passed to the compiler, incremental builds now take as long as clean builds, which is not fun if you are a WebKit developer and actually need to make changes to it. Unifying more files together will always make incremental builds slower. After some experimentation, Apple determined that, for WebKit, the optimal number of files to include together is roughly eight. At this point, there’s not yet much negative impact on incremental builds, and past here there are diminishing returns in clean build improvement.

In WebKit’s implementation, the files to bundle together are computed automatically at build time using CMake black magic. Adding a new file to the build can change how the files are bundled together, potentially causing build errors in different files if there are symbol clashes. But this is usually easy to fix, because only files from the same directory are bundled together, so random unrelated files will never be built together. The bundles are always the same for everyone building the same version of WebKit, so you won’t see random build failures; only developers who are adding new files will ever have to deal with name conflicts.

To significantly reduce name conflicts, we now limit the scope of using statements. That is, stuff like this:

using namespace JavaScriptCore;
namespace WebCore {

Has been changed to this:

namespace WebCore {
using namespace JavaScriptCore;
// ...

Some files need to be excluded due to unsolvable name clashes. For example, files that include X11 headers, which contain lots of unnamespaced symbols that conflict with WebCore symbols, don’t really have any chance. But only a few files should need to be excluded, so this does not have much impact on build time. We’ve also opted to not unify most of the GLib API layer, so that we can continue to use conventional GObject names in our implementation, but again, the impact of not unifying a few files is minimal.

We still have some room for further performance improvement, because some significant parts of the build are still not unified, including most of the WebKit layer on top. But I suspect developers who have to regularly build WebKit will already be quite pleased.

By Michael Catanzaro at February 17, 2018 07:07 PM

February 16, 2018

Michael Catanzaro: On Python Shebangs

Igalia WebKit

So, how do you write a shebang for a Python program? Let’s first set aside the python2/python3 issue and focus on whether to use env. Which of the following is correct?

#!/usr/bin/env python

The first option seems to work in all environments, but it is banned in popular distros like Fedora (and I believe also Debian, but I can’t find a reference for this). Using env in shebangs is dangerous because it can result in system packages using non-system versions of python. python is used in so many places throughout modern systems, it’s not hard to see how using #!/usr/bin/env in an important package could badly bork users’ operating systems if they install a custom version of python in /usr/local. Don’t do this.

The second option is broken too, because it doesn’t work in BSD environments. E.g. in FreeBSD, python is installed in /usr/local/bin. So FreeBSD contributors have been upstreaming patches to convert #!/usr/bin/python shebangs to #!/usr/bin/env python. Meanwhile, Fedora has begun automatically rewriting #!/usr/bin/env python to #!/usr/bin/python, but with a warning that this is temporary and that use of #!/usr/bin/env python will eventually become a fatal error causing package builds to fail.

So obviously there’s no way to write a shebang that will work for both major Linux distros and major BSDs. #!/usr/bin/env python seems to work today, but it’s subtly very dangerous. Lovely. I don’t even know what to recommend to upstream projects.

Next problem: python2 versus python3. By now, we should all be well-aware of PEP 394. PEP 394 says you should never write a shebang like this:

#!/usr/bin/env python

unless your python script is compatible with both python2 and python3, because you don’t know what version you’re getting. Your python script is almost certainly not compatible with both python2 and python3 (and if you think it is, it’s probably somehow broken, because I doubt you regularly test it with both). Instead, you should write the shebang like this:

#!/usr/bin/env python2
#!/usr/bin/env python3

This works as long as you only care about Linux and BSDs. It doesn’t work on macOS, which provides /usr/bin/python and /usr/bin/python2.7, but still no /usr/bin/python2 symlink, even though it’s now been six years since PEP 394. It’s hard to understate how frustrating this is.

So let’s say you are WebKit, and need to write a python script that will be truly cross-platform. How do you do it? WebKit’s scripts are only needed (a) during the build process or (b) by developers, so we get a pass on the first problem: using /usr/bin/env should be OK, because the scripts should never be installed as part of the OS. Using #!/usr/bin/env python — which is actually what we currently do — is unacceptable, because our scripts are python2 and that’s broken on Arch, and some of our developers use that. Using #!/usr/bin/env python2 would be dead on arrival, because that doesn’t work on macOS. Seems like the option that works for everyone is #!/usr/bin/env python2.7. Then we just have to hope that the Python community sticks to its promise to never release a python2.8 (which seems likely).


By Michael Catanzaro at February 16, 2018 08:21 PM

February 07, 2018

Workers at Your Service

Surfin’ Safari

Update: A previous version of this post stated the Service Worker API is available in all applications using WKWebView. At this time it is only available in Safari, applications that use SFSafariViewController, and web applications saved to your home screen.

The Service Worker API exposes persistent background processing capabilities to web pages. Support is available in Safari Technology Preview 48, macOS High Sierra 10.13.4 and iOS 11.3 beta seed 2. While WebKit’s implementation and feature set is quickly evolving, we believe it has reached an important milestone in terms of functionality and compliance: applications using service workers for offline support or network/cache optimizations run successfully on latest WebKit builds. Let’s now dive into the specifics of the WebKit Service Worker API implementation.

By specification, service workers and service worker clients are partitioned by their origin. To prevent user cross-site tracking, WebKit further partitions service workers and service worker clients by the top level document origin, the origin shown in the address bar. Frames that are same origin as the top level document will behave the same as in other browser engines. WebKit behaves differently for cross-origin frames. A service worker registered by an iframe inside a page will be able to communicate to all service workers and clients that share the same (, partition, but not to any other or client. A network load made by a (, service worker will use the same cookies as if the network load was made in an frame embedded in a page. Similarly, private browsing mode is enforced in a service worker by partitioning service workers according the browsing session.

The Service Worker API is implemented in WebKit’s multi-process infrastructure which offers both security and performance benefits. Service worker instances run in an isolated service worker process. This process is similar to WebContent processes responsible for rendering web pages and executing arbitrary JavaScript. A separate process, the Storage process, handles the registration, persistency and lifecycle of service workers. As a service worker instance consumes both memory and CPU time, it is important to run them when needed only. Service workers are typically started when being initially registered by a web page. In normal conditions, a service worker will be terminated when there is no service worker client in its partition after a small grace period. Service workers are restarted whenever some interaction is needed, typically in case of postMessage or fetch events.

The Cache API allows storing fetch requests and responses persistently. This is a key API for offline support and proxy-based network optimizations. Similarly to service workers, caches are partitioned by (top origin, frame origin) and browsing session. The current Cache API quota is set to a fixed value of 50 MiB per partition. Once this limit is reached, the web application needs to evict cache entries in order to free space. Both service worker and cache persistent information can be cleared with WebKit APIs. In Safari Technology Preview, this information is put in the ‘Cache’ category of the Privacy preference pane.

Service worker and Cache API stored information will grow as a user is browsing content. To keep only the stored information that is useful to the user, WebKit will remove unused service worker registrations after a period of a few weeks. Caches that do not get opened after a few weeks will also be removed. Web Applications must be resilient to any individual cache, cache entry or service worker being removed.

Web Inspector supports debugging service workers. The ‘Develop’ menu contains the list of running service workers at any time. When clicking on one of the service worker entries, an inspector will be attached to the service worker. From here, you can debug code related to fetch or postMessage events by using breakpoints. The inspector console is also a great place to trigger network loads in the context of the service worker using the fetch API. The service worker caches can be inspected from the console as well with a few lines of code.

We are excited to see service worker applications coming to WebKit and Apple platforms. We encourage you to try the latest implementation and feature set available in Safari Technology Preview 48, macOS High Sierra 10.13.4 beta seed 2, and iOS 11.3 beta seed 2. We want to hear your feedback! File a bug, email, or tweet to @webkit.

February 07, 2018 09:00 PM

Release Notes for Safari Technology Preview 49

Surfin’ Safari

Safari Technology Preview Release 49 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 227071-227873.

Service Workers

  • Changed Service Workers restored from persistent storage to have “activated” state (r227153)
  • Changed to terminate Service Workers that are unresponsive (r227174)
  • Prevented Service Worker registrations restored from disk from being reused when the JavaScript calls register() again (r227220)


  • Added support for ConsumeData callback when chunk data is received for Fetch response (r227870)
  • Changed opaque being-loaded responses to clone their body (r227581)
  • Filtered out Fetch headers from an opaque response (r227339)
  • Fixed Fetch redirect to be compatible with “no-cors” mode (r227270)
  • Fixed Fetch response to copy its URL from the request if it is null (r227531)
  • Set integrity Fetch options for loading scripts and CSS (r227612)

Intelligent Tracking Prevention

  • Blocked cookies for prevalent resources without user interaction (r227103)
  • Ensured ServiceWorker loading and requests are correctly cleared by Intelligent Tracking Prevention (r227358)
  • Introduced debug mode as experimental feature (r227762)


  • Added support for percentages in column-gap (r227676)
  • Added support for parsing calc() in CSS media queries (r227295)
  • Adopted CSS WG recommended syntax changes to remove "left" and "right" in block/cross-axis alignment properties (r227432)
  • Adopted CSS WG recommended syntax changes requiring overflow-position to precede
    self-position or content-position in the css-align property (r227297)
  • Adopted support for a recent specification change removing "baseline" as a valid value for the ‘justify-content’ property (r227786)
  • Fixed computing the scroll position of position:fixed elements when the scale is greater than 1 (r227430)
  • Preserved original image and picture element colors when invert colors is on (r227219)


  • Fixed the overflow of formulas for display mathematics (r227722)
  • Optimized building the non-fast scrollable region with multiple iframes (r227396)


  • Fixed the feMorphology SVG filter to allow the radius on one axis to be 0 and still apply the effect (r227440)


  • Implemented trimStart and trimEnd (r227779)
  • Relaxed line terminators in String to make JSON subset of JavaScript (r227775)

Web Inspector

  • Changed clicking on a path component that has no siblings to now select it (r227108)
  • Changed the Layers tab to use a statically positioned layer details panel instead of a moving popover (r227244)
  • Changed the Styles sidebar to always display CSS rules left-to-right, even when Web Inspector uses RTL layout (r227228)
  • Fixed an issue that caused the Canvas Tab to display multiple “waiting for frames” messages (r227243)
  • Fixed an issue that cause the record button on a Canvas Tab canvas to sometimes not appear on hover (r227155)
  • Fixed a bug that caused the Network Tab sort indicator to hide when a sorted column is hidden and re-shown (r227667)
  • Fixed the Network Tab’s table columns to no longer shake when scrolling at non-default zoom levels (r227463)
  • Fixed a data corruption issue triggered by updating values in the Styles Sidebar quickly (r227370)
  • Fixed the Styles sidebar to stop throwing exceptions when tabbing past commented out properties (r227232)
  • Fixed the Resource Tab detail sidebar to wrap super long URLs better (r227072)
  • Fixed Window resizing when the Web Inspector is detached from the browser (r227429)
  • Prevented showing “Displayed Columns” when right-clicking in a table header if all columns are required (r227652)
  • Improved the behavior of the Cookies table in the Network Tab at narrow widths (r227666)
  • Improved Navigation Bar layout at narrow heights (r227707)


  • Added support of multi keys from different sessions in CDMinstanceClearKey (r227409)
  • Changed to resign the NowPlaying status when no media element is eligible (r227373, r227457)
  • Changed to use existing RGB colorspace instead of creating a new one (r227094)
  • Fixed cues for WebVTT served via HLS (r227121)


  • Added a deprecation warning to the Console when AppCache is used (r227225)
  • Added console messages for cache storage errors like Quota (r227245)
  • Changed to not use the storage process when loading a main resource if there is no Service Worker registered (r227161)
  • Changed to not use the storage process when registering a Service Worker client if there is no Service Worker registered (r227242)
  • Ensured Cache API will resolve promises in the same order as called (r227768)
  • Fixed DOMCache data not getting properly removed when clearing data for a given origin (r227269)
  • Increased default cache storage quota to 50MB (r227298)


  • Added a policy check for targeted windows when navigating to a JavaScript URL (r227567)
  • Added CSP post checks for Service Worker responses (r227680)
  • Disabled access to Service Workers and the Cache API in sandboxed frames without the allow-same-origin flag (r227639)
  • Updated frame-ancestor directive to match Content Security Policy Level 3 (r227238)


  • Added support for ARIA active-descendant (r227144)
  • Added a way for VoiceOver to uniquely identify a web session (r227526)
  • Implemented support for Graphics ARIA roles: graphics-document, graphics-object,
    and graphics-symbol (r227344)
  • Prevented SVG AAM mapping from overriding ARIA role attribute in the case of SVG root (r227536)

Bug Fixes

  • Fixed the GitHub login at by ensuring redirections for subresource loads can change Service Worker controllers (r227348)
  • Fixed blob conversion and sanitization for Microsoft Word for Mac 2011 (r227351)
  • Prevented a disallowed user-installed font from being used if its PostScript name is specified (r227776)

February 07, 2018 06:00 PM

January 24, 2018

Michael Catanzaro: Announcing Epiphany Technology Preview

Igalia WebKit

If you use macOS, the best way to use a recent development snapshot of WebKit is surely Safari Technology Preview. But until now, there’s been no good way to do so on Linux, short of running a development distribution like Fedora Rawhide.

Enter Epiphany Technology Preview. This is a nightly build of Epiphany, on top of the latest development release of WebKitGTK+, running on the GNOME master Flatpak runtime. The target audience is anyone who wants to assist with Epiphany development by testing the latest code and reporting bugs, so I’ve added the download link to Epiphany’s development page.

Since it uses Flatpak, there are no host dependencies asides from Flatpak itself, so it should work on any system that can run Flatpak. Thanks to the Flatpak sandbox, it’s far more secure than the version of Epiphany provided by your operating system. And of course, you enjoy automatic updates from GNOME Software or any software center that supports Flatpak.


(P.S. If you want to use the latest stable version instead, with all the benefits provided by Flatpak, get that here.)

By Michael Catanzaro at January 24, 2018 10:58 PM

Release Notes for Safari Technology Preview 48

Surfin’ Safari

Safari Technology Preview Release 48 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 226358-227071.

Password AutoFill

  • Disabled Automatic AutoFill of user names and passwords at page load to prevent sharing information without user consent

Storage Access API

  • Enabled the Storage Access API by default (r226418, r226669)
  • Changed to remove access for all frames under a page when the page is closed (r226542)


  • Fixed SVG lighting filter lights to use the correct coordinate system (r226363)
  • Fixed feLighting that has a filter primitiveUnits="objectBoundingBox" (r226373)

Service Workers

  • Added CSP support to Service Workers (r226628)
  • Changed to use no-cache fetch mode when loading main documents with location.reload() (r226745)
  • Changed WebProcess to pass the registration identifier and not the worker identifier for fetch events (r226904)
  • Changed to use Service Workers for documents with data URLs or blob URLs (r226361)
  • Changed behavior to cancel pending script loads when the Service Worker is being terminated (r226398)
  • Cleared the Cache volatile storage as a memory optimization. (r227052)
  • Exposed redirect mode as “manual” for navigation loads in Service Workers (r226400)
  • Enabled User Timing and Resource Timing for Service Workers (r226451)
  • Fixed fetch events getting sent to a Service Worker before its state is set to “activated” (r227070)
  • Fixed navigator.onLine inside Service Workers (r226510)
  • Implemented the “main fetch” default referrer policy setting (r226397)
  • Made Service Workers behave correctly with regards to Page Cache (r226677)
  • Stopped exposing fetch and extendable events to window (r226526)


  • Fixed ::first-letter to select the correct grapheme pairs (r226614)
  • Fixed a blank pages except for inner iframes when pending stylesheets cause style.isNotFinal() to be true (r226653)
  • Fixed image-rendering to affect the scaling of border-image (r226957)
  • Fixed the special list-item counter to start from the correct number for ::before and ::after (r226613, r226675)
  • Improved text appearance on some CSS spec pages (r227000)


  • Changed redirected iframes loading with request.redirect=follow to fail (r226792)
  • Fixed setting window.opener to null to disown its opener (r226842)
  • Implemented createImageBitmap(ImageBitmap) (r226500)
  • Implemented Cache API partitioning based on ClientOrigin (r226481)
  • Made elements with zero width or height focusable (r226823)


  • Fixed constant frame dropping during Flash video playback (r226369)
  • Fixed clipping copyTexImage2D and copyTexSubImage2D (r226490)
  • Fixed a visual flash caused by using font-display:fallback (r226668)
  • Fixed data URL fonts that are split in the middle of an alphabet from causing random letters to disappear (r226930)

Web Inspector

  • Added support for JSX (React) syntax highlighting (r226909)
  • Added a content menu to the main Tab bar for showing and hiding tabs (r226963)
  • Fixed the “Log Value” context menu sometimes being unavailable (r226394)
  • Fixed typing a “space” in the quick console triggering a Canvas recording (r227008)
  • Fixed fuzzy Capture Element screenshots (r226425)
  • Fixed the Find banner sometimes not working when already populated and shown for first time on a resource (r226380)
  • Fixed the “find next” and “find previous” within a resource content view does bouncing highlight when the editor scrolls (r226517)
  • Fixed Layers sidebar to hide popovers when it is collapsed (r226671)
  • Fixed the Export HAR context menu in the Network tab (r226992)
  • Fixed DOM Tree Element selection in RTL mode (r226392)
  • Fixed clicking on white space after a property sometimes placing a blank property at the wrong index in the Styles sidebar (r226994)
  • Fixed long values causing bad wrapping in the Styles sidebar (r226995)
  • Fixed pressing the down key to select the first item from completion list when focusing on an empty value (r226996)
  • Fixed Command-G (⌘G) and Shift-Command-G (⇧⌘G) text search after closing the find banner (r226415)
  • Fixed the Debugger tab to restore the selected resource on reload (r226374)
  • Improved performance when dragging the recording slider in the Canvas tab (r226755)
  • Improved inspector launch time, especially for systems with many fonts (r226371)
  • Made the Console’s Execution Context picker stand out when it is non-default (r227003)
  • Prevented properties from being semitransparent or crossed out while editing in the Styles sidebar (r226939)

Web Driver

  • Implemented the Get Timeouts command (r226770)


  • Changed the style of video elements when invert colors is on to preserve normal video colors (r226825)
  • Implemented the updated CSS3 Speech for the speak and speak-as properties (r226432)


  • Changed RTCController to disable ICE candidate filtering in case of getUserMedia based on the RTCPeerConnection origin (r226804)
  • Updated WebRTC to close sockets that are marked as defunct (r226475)


  • Applied poisoning to pointers in JavaScriptCore (r226530)
  • Fixed for-in caching when indexed properties are added to properties on the prototype chain (r226767)
  • Fixed Array storage operations that sometimes do not update the indexing mask correctly (r226416)
  • Removed the arguments and caller properties for bound functions in Object.getOwnPropertyNames (r226489)


  • Added poison to JavaScript object’s secrets (r226485)

Bug Fixes

  • Changed the History state to be updated during client redirects with asynchronous policy decisions (r226929)
  • Forbid “<” and “>” in the host name of a URL (r226469)
  • Prevented recording dynamic spelling corrections while in an ephemeral browsing session (r226644)
  • Reduced the precision of “high” resolution time to 1ms (r226495)

January 24, 2018 06:00 PM

January 15, 2018

Speedometer 2.0: A Benchmark for Modern Web App Responsiveness

Surfin’ Safari

In 2014, the WebKit team at Apple released Speedometer 1.0, a benchmark for web app responsiveness. It simulates user interactions in web applications, using TodoMVC to orchestrate adding, completing, and removing todo items. Speedometer repeats these actions using DOM APIs that were extensively used in real-world applications. The performance of these kinds of operations depends on the speed of the JavaScript engine, DOM APIs, layout, CSS style resolution and other parts of the browser engine.

Browser engineers have been optimizing their engines using Speedometer as a proxy for real-world use of popular frameworks for a number of years. Originally, Speedometer included implementations of todo apps in six popular JavaScript frameworks and libraries in heavy use: Ember, Backbone, AngularJS, jQuery, Flight, and an early version of React. It also included vanilla JavaScript.

The web developer ecosystem has evolved significantly since Speedometer 1.0 was first released, as have the trends in what libraries, frameworks, and programming paradigms are used. Developers now commonly use transpilers, module bundlers, and recently-introduced frameworks when creating new sites. This is why, for the last year, engineers from WebKit and Chromium have been collaborating on a new version of Speedometer that better reflects the frameworks, tools, and patterns in wide use today.

Today, we are pleased to announce the Speedometer 2.0 benchmark. We hope this new version of Speedometer helps browser vendors optimize their browser engines for the modern Web.

Support for modern JavaScript frameworks and libraries

Over the last three years, a growing number of real-world sites have been written using React — a JavaScript library for authoring user interfaces. Derivatives such as Preact and Inferno have also gained popularity. Speedometer 2.0 includes web apps implemented using these libraries. It also includes an entry using React and Redux — a popular state management library.

Webpack and Rollup are popular JavaScript module bundlers frequently used with these libraries and Speedometer 2.0 includes output generated by these tools.

Ember.js, which featured in the original Speedometer, now has a dedicated tool to create new projects, and provides a more streamlined deployment process for authors. In addition, there were large changes to the core Ember framework over the years. To incorporate these changes in Ember.js itself and the way developers use Ember.js today, Speedometer 2.0 includes an implementation using the latest Ember, built using Ember CLI.

Another framework we observed gaining traction is Vue.js — a progressive solution aimed at being incrementally adoptable. Similar to Ember, Vue.js has prescriptive tooling for getting started and Speedometer 2.0 includes a Vue.js implementation built using the Vue CLI.

It’s of course true that not all real-world sites are being built using these solutions. Many are still deployed using libraries that were popular when Speedometer 1.0 was authored, which is one reason Speedometer 2.0 also includes updates to implementations written in AngularJS, Backbone.js, and Flight.

ES2015 JavaScript and Babel support

Speedometer 1.0 included a version of the todo app implemented with vanilla JavaScript — i.e. without using any libraries or frameworks. At the time, web developers primarily wrote their applications in the version of JavaScript known as ES5. Today, modern browsers have excellent support of ES2015 (also known as ES6), a more evolved version of JavaScript. Speedometer 2.0 now includes a todo app implemented using ES2015 features like classes, const, let, arrow functions, and template literals.

Although measuring vanilla JavaScript performance has high value, a growing number of developers today also use transpilers like Babel to transpile the latest versions of JavaScript code back to a version supporting all browsers they care about. To reflect this workflow, Speedometer 2.0 includes an ES2015 implementation that uses ES Modules and has ES5 output generated by Babel. In the future, as browsers gain full support for native ES Modules, we hope to evolve the benchmark to also track an implementation that isn’t bundled or translated.

TypeScript support

TypeScript is a typed superset of JavaScript that has been gaining traction in the web developer community. It offers types as a first-class syntax, generally fast compilation, and rich tooling for type-aware auto-completion and error highlighting during iteration.

Today, one of the largest users of TypeScript is Angular. To enable browsers to measure the kinds of output a TypeScript app might generate, Speedometer 2.0 includes an Angular implementation written in TypeScript, transpiled to ES5. We’re hopeful that browsers optimizing for this implementation will be able to offer the same wins as more frameworks introduce TypeScript support.

Future-facing: functional programming

The front-end developer community has been shifting in the direction of borrowing more patterns from functional programming. This has been demonstrated with the growth of interest in technologies like Elm and PureScript, both of which transpile down to JavaScript. To enable browsers to optimize for these patterns, Speedometer 2.0 includes implementations for both of these technologies.

Updates in score calculation

Speedometer 1.0 calculated a final score for Web App Responsiveness using the arithmetic mean of the run time needed to add, mark completed, and remove 100 todo items in each implementation in order to incentivize browser vendors to optimize the slowest framework or library. Unfortunately, this resulted in some implementation of a todo app getting 25× more weight compared to another as we added more libraries and frameworks to Speedometer 2.0. It became particularly problematic when we added back a debug build of Ember — it was more than 4× slower than the Ember production build. However, only a small fraction of websites deployed with Ember use debug builds.

In Speedometer 2.0, we’ve changed the score to be computed as the geometric mean against different implementations of the todo app. The final score is computed as the arithmetic mean of the geometric means computed for each iteration of the benchmark.


Speedometer 2.0 has been an exciting collaboration between browser vendors. We would like to build on this collaboration in future iterations of the benchmark by working more closely with framework authors and the developer community to identify broadly-used patterns, frameworks, and tools for which browser engines could be optimized.

January 15, 2018 06:00 PM

January 11, 2018

Frédéric Wang: Review of Igalia's Web Platform activities (H2 2017)

Igalia WebKit

Last september, I published a first blog post to let people know a bit more about Igalia’s activities around the Web platform, with a plan to repeat such a review each semester. The present blog post focuses on the activity of the second semester of 2017.


As part of Igalia’s commitment to diversity and inclusion, we continue our effort to standardize and implement accessibility technologies. More specifically, Igalian Joanmarie Diggs continues to serve as chair of the W3C’s ARIA working group and as an editor of Accessible Rich Internet Applications (WAI-ARIA) 1.1, Core Accessibility API Mappings 1.1, Digital Publishing WAI-ARIA Module 1.0, Digital Publishing Accessibility API Mappings 1.0 all of which became W3C Recommandations in December! Work on versions 1.2 of ARIA and the Core AAM will begin in January. Stay tuned for the First Public Working Drafts.

We also contributed patches to fix several issues in the ARIA implementations of WebKit and Gecko and implemented support for the new DPub ARIA roles. We expect to continue this collaboration with Apple and Mozilla next year as well as to resume more active maintenance of Orca, the screen reader used to access graphical desktop environments in GNU/Linux.

Last but not least, progress continues on switching to Web Platform Tests for ARIA and “Accessibility API Mappings” tests. This task is challenging because, unlike other aspects of the Web Platform, testing accessibility mappings cannot be done by solely examining what is rendered by the user agent. Instead, an additional tool, an “Accessible Technology Test Adapter” (ATTA) must be also be run. ATTAs work in a similar fashion to assistive technologies such as screen readers, using the implemented platform accessibility API to query information about elements and reporting what it obtains back to WPT which in turn determines if a test passed or failed. As a result, the tests are currently officially manual while the platform ATTAs continue to be developed and refined. We hope to make sufficient progress during 2018 that ATTA integration into WPT can begin.


This semester, we were glad to receive Bloomberg’s support again to pursue our activities around CSS. After a long commitment to CSS and a lot of feedback to Editors, several of our members finally joined the Working Group! Incidentally and as mentioned in a previous blog post, during the CSS Working Group face-to-face meeting in Paris we got the opportunity to answer Microsoft’s questions regarding The Story of CSS Grid, from Its Creators (see also the video). You might want to take a look at our own videos for CSS Grid Layout, regarding alignment and placement and easy design.

On the development side, we maintained and fixed bugs in Grid Layout implementation for Blink and WebKit. We also implemented alignment of positioned items in Blink and WebKit. We have several improvements and bug fixes for editing/selection from Bloomberg’s downstream branch that we’ve already upstreamed or plan to upstream. Finally, it’s worth mentioning that the work done on display: contents by our former coding experience student Emilio Cobos was taken over and completed by antiik (for WebKit) and rune (for Blink) and is now enabled by default! We plan to pursue these developments next year and have various ideas. One of them is improving the way grids are stored in memory to allow huge grids (e.g. spreadsheet).

Web Platform Predictability

One of the area where we would like to increase our activity is Web Platform Predictability. This is obviously essential for our users but is also instrumental for a company like Igalia making developments on all the open source Javascript and Web engines, to ensure that our work is implemented consistently across all platforms. This semester, we were able to put more effort on this thanks to financial support from Bloomberg and Google AMP.

We have implemented more frame sandboxing attributes WebKit to improve user safety and make control of sandboxed documents more flexible. We improved the sandboxed navigation browser context flag and implemented the new allow-popup-to-escape-sandbox, allow-top-navigation-without-user-activation, and allow-modals values for the sandbox attribute.

Currently, HTML frame scrolling is not implemented in WebKit/iOS. As a consequence, one has to use the non-standard -webkit-overflow-scrolling: touch property on overflow nodes to emulate scrollable elements. In parallel to the progresses toward using more standard HTML frame scrolling we have also worked on annoying issues related to overflow nodes, including flickering/jittering of “position: fixed” nodes or broken Find UI or a regression causing content to disappear.

Another important task as part of our CSS effort was to address compatibility issues between the different browsers. For example we fixed editing bugs related to HTML List items: WebKit’s Bug 174593/Chromium’s Issue 744936 and WebKit’s Bug 173148/Chromium’s Issue 731621. Inconsistencies in web engines regarding selection with floats have also been detected and we submitted the first patches for WebKit and Blink. Finally, we are currently improving line-breaking behavior in Blink and WebKit, which implies the implementation of new CSS values and properties defined in the last draft of the CSS Text 3 specification.

We expect to continue this effort on Web Platform Predictability next year and we are discussing more ideas e.g. WebPackage or flexbox compatibility issues. For sure, Web Platform Tests are an important aspect to ensure cross-platform inter-operability and we would like to help improving synchronization with the conformance tests of browser repositories. This includes the accessibility tests mentioned above.


Last November, we launched a fundraising Campaign to implement MathML in Chromium and presented it during Frankfurt Book Fair and TPAC. We have gotten very positive feedback so far with encouragement from people excited about this project. We strongly believe the native MathML implementation in the browsers will bring about a huge impact to STEM education across the globe and all the incumbent industries will benefit from the technology. As pointed out by Rick Byers, the web platform is a commons and we believe that a more collective commitment and contribution are essential for making this world a better place!

While waiting for progress on Chromium’s side, we have provided minimal maintenance for MathML in WebKit:

  • We fixed all the debug ASSERTs reported on Bugzilla.
  • We did follow-up code clean up and refactoring.
  • We imported Web Platform tests in WebKit.
  • We performed review of MathML patches.

Regarding the last point, we would like to thank Minsheng Liu, a new volunteer who has started to contribute patches to WebKit to fix issues with MathML operators. He is willing to continue to work on MathML development in 2018 as well so stay tuned for more improvements!


During the second semester of 2017, we worked on the design, standardization and implementation of several JavaScript features thanks to sponsorship from Bloomberg and Mozilla.

One of the new features we focused on recently is BigInt. We are working on an implementation of BigInt in SpiderMonkey, which is currently feature-complete but requires more optimization and cleanup. We wrote corresponding test262 conformance tests, which are mostly complete and upstreamed. Next semester, we intend to finish that work while our coding experience student Caio Lima continues work on a BigInt implementation on JSC, which has already started to land. Google also decided to implement that feature in V8 based on the specification we wrote. The BigInt specification that we wrote reached Stage 3 of TC39 standardization. We plan to keep working on these two BigInt implementations, making specification tweaks as needed, with an aim towards reaching Stage 4 at TC39 for the BigInt proposal in 2018.

Igalia is also proposing class fields and private methods for JavaScript. Similarly to BigInt, we were able to move them to Stage 3 and we are working to move them to stage 4. Our plan is to write test262 tests for private methods and work on an implementation in a JavaScript engine early next year.

Igalia implemented and shipped async iterators and generators in Chrome 63, providing a convenient syntax for exposing and using asynchronous data streams, e.g., HTML streams. Additionally, we shipped a major performance optimization for Promises and async functions in V8.

We implemented and shipped two internationalization features in Chrome, Intl.PluralRules and Intl.NumberFormat.prototype.formatToParts. To push the specifications of internationalization features forwards, we have been editing various other internationalization-related specifications such as Intl.RelativeTimeFormat, Intl.Locale and Intl.ListFormat; we also convened and led the first of what will be a monthly meeting of internationalization experts to propose and refine further API details.

Finally, Igalia has also been formalizing WebAssembly’s JavaScript API specification, which reached the W3C first public working draft stage, and plans to go on to improve testing of that specification as the next step once further editorial issues are fixed.


Thanks to sponsorship from Mozilla we have continued our involvement in the Quantum Render project with the goal of using Servo’s WebRender in Firefox.

Support from Metrological has also given us the opportunity to implement more web standards from some Linux ports of WebKit (GTK and WPE, including:

  • WebRTC
  • WebM
  • WebVR
  • Web Crypto
  • Web Driver
  • WebP animations support
  • HTML interactive form validation
  • MSE


Thanks for reading and we look forward to more work on the web platform in 2018. Onwards and upwards!

January 11, 2018 11:00 PM

January 10, 2018

Manuel Rego: "display: contents" is coming

Igalia WebKit

Yes, display: contents is enabled by default in Blink and WebKit and it will be probably shipped in Chrome 65 and Safari 11.1. These browsers will join Firefox that is shipping it since version 37, which makes Edge the only one missing the feature (you can vote for it!).

Regarding this I’d like to highlight that the work to support it in Chromium was started by Emilio Cobos during his Igalia Coding Experience that took place from fall 2016 to summer 2017.

You might (or not) remember a blog post from early 2016 where I was talking about the Igalia Coding Experience program and some ideas of tasks to be done as part of the Web Platform team. One of the them was display: contents which is finally happening.

What is display: contents?

This new value for the display property allows you to somehow remove an element from the box tree but still keep its contents. The proper definition from the spec:

The element itself does not generate any boxes, but its children and pseudo-elements still generate boxes and text runs as normal. For the purposes of box generation and layout, the element must be treated as if it had been replaced in the element tree by its contents (including both its source-document children and its pseudo-elements, such as ::before and ::after pseudo-elements, which are generated before/after the element’s children as normal).

A simple example will help to understand it properly:

<div style="display: contents;
            background: magenta; border: solid thick black; padding: 20px;
            color: cyan; font: 30px/1 Monospace;">
  <span style="background: black;">foobar</span>

display: contents makes that the div doesn’t generate any box, so its background, border and padding are not renderer. However the inherited properties like color and font have effect on the child (span element) as expected.

For this example, the final result would be something like:

<span style="background: black; color: cyan; font: 30px/1 Monospace;">foobar</span>







Unsupported vs actual (in your browser) vs supported output for the previous example

If you want more details Rachel Andrew has a nice blog post about this topic.

CSS Grid Layout & display: contents

As you could expect from a post from myself this is somehow related to CSS Grid Layout. 😎 display: contents can be used as a replacement of subgrids (which are not supported by any browser at this point) in some use cases. However subgrids are still needed for other scenarios.

The canonical example for Grid Layout auto-placement is a simple form like:

  form   { display:     grid;   }
  label  { grid-column: 1;      }
  input  { grid-column: 2;      }
  button { grid-column: span 2; }
  <label>Name</label><input />
  <label>Mail</label><input />

A simple form formatted with CSS Grid Layout A simple form formatted with CSS Grid Layout

However this is not the typical HTML of a form, as you usually want to use a list inside, so people using screen readers will know how many fields they have to fill in your form beforehand. So the HTML looks more like this:

    <li><label>Name</label><input /></li>
    <li><label>Mail</label><input /></li>

With display: contents you’ll be able to have the same layout than in the first case with a similar CSS:

ul     { display: grid;       }
li     { display: contents;   }
label  { grid-column: 1;      }
input  { grid-column: 2;      }
button { grid-column: span 2; }

So this is really nice, now when you convert your website to start using CSS Grid Layout, you would need less changes on your HTML and you won’t need to remove some HTML that is really useful, like the list in the previous example.

Chromium implementation

As I said in the introduction, Firefox shipped display: contents three years ago, however Chromium didn’t have any implementation for it. Igalia as CSS Grid Layout implementor was interested in having support for the feature as it’s a handy solution for several Grid Layout use cases.

The proposal for the Igalia Coding Experience was the implementation of display: contents on Blink as the main task. Emilio did an awesome job and managed to implement most of it, reporting issues to CSS Working Group and other browsers as needed, and writing tests for the web-platform-tests repository to ensure interoperability between the implementations.

Once the Coding Experience was over there were still a few missing things to be able to enable display: contents by default. Rune Lillesveen (Google and previously Opera) who was helping during the whole process with the reviews, finished the work and shipped it past week.

WebKit implementation

WebKit already had an initial support for display: contents that was only used internally by Shadow DOM implementation and not exposed to the end users, neither supported by the rest of the code.

We reactivated the work there too, he didn’t have time to finish the whole thing but later Antti Koivisto (Apple) completed the work and enabled it by default on trunk by November 2017.


Igalia is one of the top external contributors on the open web platform projects. This put us on a position that allows us to implement new features in the different open source projects, thanks to our community involvement and internal knowledge after several years of experience on the field. Regarding display: contents implementation, this feature probably wouldn’t be available today in Chromium and WebKit without Igalia’s support, in this particular case through a Coding Experience.

We’re really happy about the results of the Coding Experience and we’re looking forward to repeat the success story in the future.

Of course, all the merit goes to Emilio, who is an impressive engineer and did a great job during the Coding Experience. As part of this process he got committer privileges in both Chromium and WebKit projects. Kudos!

Last, but not least, thanks to Antti and Rune for finishing the work and making display: contents available to WebKit and Chromium users.

January 10, 2018 11:00 PM

Release Notes for Safari Technology Preview 47

Surfin’ Safari

Safari Technology Preview Release 47 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 225841-226358.

This release contains the Spectre mitigations released in iOS 11.2.2, the High Sierra 10.13.2 supplemental update, and Safari 11.0.2 reissue released on Monday, January 8. For more information about Spectre, see What Spectre and Meltdown Mean For WebKit.

Storage Access API

This is a newly proposed API (WhatWG issue) that can be enabled in the Develop menu under Experimental Features. Cookies partitioned by Safari’s Intelligent Tracking Prevention can be accessed in an iframe loaded from the cookie’s domain by calling document.requestStorageAccess() in a click event handler. When the returned promise resolves, the first-party cookies in that iframe will be accessible. There is also the convenience function document.hasStorageAccess() available that doesn’t require a click.

  • Enabled allowing requests from non-sandboxed <iframes> (r226244)
  • Implemented frame-specific access in the document.cookie layer (r225934)
  • Made document.hasStorageAccess() retrieve the current status from the network process (r226016)
  • Refactored XPC for access removal to go straight from the web process to the network process (r226389)

Service Workers

  • Added support for response blob given to fetch events (r226066)
  • Changed extracting a body of type Blob to set the Content-Type to null instead of an empty string (r226162)
  • Changed to use “error” redirect mode for fetching service worker scripts (r226087)
  • Changed the Service Worker script fetch request to set the Service-Worker header (r225996)
  • Changed Service Worker to not clean HTTP headers added by the application or by Fetch specification before Service Worker interception (r226126)
  • Fixed the default scope used when registering a service worker (r226096)
  • Fixed the Service Worker Registration promise sometimes not getting rejected when the script load fails (r225975)
  • Fixed Service Worker served response tainting to keep its tainting (r226090)
  • Fixed scopeURL to start with the provided scriptURL (r226141)
  • Fixed self.importScripts() to obey updateViaCache inside service workers (r225940)
  • Fixed Fetch handling to wait for the Service Worker’s state to become activated (r226136)
  • Fixed SameOrigin and CORS fetch to fail on opaque responses served from a Service Worker (r226084)
  • Fixed memory cache to not reuse resources with a different credential fetch option (r226333)
  • Prevented searching for service worker registration for non-HTTP navigation loads (r226185, r226200)
  • Supported Service Worker interception of a request with blob body (r226191)


  • Enabled picture-in-picture from an inline element on suspend (r226217)
  • Fixed playing media elements which call “pause(); play()” getting the play promise rejected (r226059, r226150)
  • Implemented <iframe allow="camera; microphone"> (r225963)


  • Fixed elements animated on-screen that are sometimes missing (r225983)
  • Fixed setting the fePointLights color (r226317)
  • Fixed the color of the bottom right pixel of feDiffuseLighting (r226316)
  • Fixed SVG lighting colors to be converted into linearSRGB (r226315)
  • Updated the SVG use element’s shadow trees explicitly before the style recall (r225868)

Web Inspector

  • Enabled the Canvas Tab by default (r225979)
  • Improved open time performance when enumerating system fonts (r226352)
  • Fixed Command-Option-R (⌘⌥R) in the docked inspector causing Web Inspector to reload instead of the inspected page (r225907)
  • Fixed the URL filter in the Network Tab to be case-insensitive like filter bars in other tabs (r225939)
  • Fixed mis-sized waterfall graphs in the Network Tab after closing the detail view (r226070)
  • Redesigned the waterfall popover showing timing data in the Network Tab table (r226158)
  • Updated the Time column in the Network Tab table to include the total duration not just the download duration (r226151)
  • Added an inline swatch for CSS variables in the Styles sidebar (r226079)
  • Added support for typing a semicolon at the end of a value to move to the next property in the Styles sidebar (r226149)
  • Enabled Command-S (⌘S) to save changes in the matching CSS resource in the Styles sidebar (r226082)
  • Fixed selecting text in the Styles sidebar to not add new properties (r225945)
  • Implemented clicking above the selector to prepend a new property in the Styles sidebar (r225968)

Clipboard API

  • Fixed isSafari runtime check to enable custom clipboard types and clipboard data sanitization in Safari Technology Preview (r226215)
  • Fixed not being able to paste images on Gmail (r226173)
  • Reverted blob URL conversions in pasted contents for LegacyWebKit clients (r226156)

Bug Fix

  • Avoided waking plugin process up unnecessarily (r225984)

Storage Access API: Refactor XPC for access removal to go straight from the web process to the network process (r226389)

By Jon Davis at January 10, 2018 06:00 PM

January 09, 2018

What Spectre and Meltdown Mean For WebKit

Surfin’ Safari

Security researchers have recently uncovered security issues known as Meltdown and Spectre. These issues apply to all modern processors and allow attackers to gain read access to parts of memory that were meant to be secret. To initiate a Spectre- or Meltdown-based attack, the attacker must be able to run code on the victim’s processor. WebKit is affected because in order to render modern web sites, any web JavaScript engine must allow untrusted JavaScript code to run on the user’s processor. Spectre impacts WebKit directly. Meltdown impacts WebKit because WebKit’s security properties must first be bypassed (via Spectre) before WebKit can be used to mount a Meltdown attack.

  • WebKit relies on branch instructions to enforce what untrusted JavaScript and WebAssembly code can do. Spectre means that an attacker can control branches, so branches alone are no longer adequate for enforcing security properties.
  • Meltdown means that userland code, such as JavaScript running in a web browser, can read kernel memory. Not all CPUs are affected by Meltdown and Meltdown is being mitigated by operating system changes. Mounting a Meltdown attack via JavaScript running in WebKit requires first bypassing branch-based security checks, like in the case of a Spectre attack. Therefore, Spectre mitigations that fix the branch problem also prevent an attacker from using WebKit as the starting point for Meltdown.

  • This document explains how Spectre and Meltdown affect existing WebKit security mechanisms and what short-term and long-term fixes WebKit is deploying to provide protection against this new class of attacks. The first of these mitigations shipped on Jan 8, 2018:

    • iOS 11.2.2.
    • High Sierra 10.13.2 Supplemental Update. This reuses the 10.13.2 version number. You can check if your Safari and WebKit are patched by verifying the full version number in About Safari. The version number should be either 13604. or 13604.
    • Safari 11.0.2 for El Capitan and Sierra. This reuses the 11.0.2 version number. Patched versions are 11604. (El Capitan) and 12604. (Sierra).

    Spectre and Security Checks

    Spectre means that branches are no longer sufficient for enforcing the security properties of read operations in WebKit. The most impacted subsystem is JavaScriptCore (WebKit’s JavaScript engine). Almost all bounds checks can be bypassed to read arbitrarily out-of-bounds. This could allow an attacker to read arbitrary memory. All type checks are also vulnerable. For example, if some type contains an integer at offset 8 while another type contains a pointer at offset 8, then an attacker could use Spectre to bypass the type check that is supposed to ensure that you can’t use the integer to craft an arbitrary pointer.

    JavaScriptCore is meant to be a secure language virtual machine. It should be possible to load untrusted JavaScript or WebAssembly code into your process without the risk of your process’s memory being leaked to the JavaScript code except in cases where you explicitly export data to JavaScript via our C or Objective-C binding API. Spectre breaks this property of JavaScriptCore because untrusted JavaScript or WebAssembly now has a theoretical path to reading all of the host process’s address space.

    DOM APIs and system APIs called by DOM APIs also use branches to enforce their security properties, and those are callable from JavaScript. Hence, Spectre is not just an attack on JavaScriptCore itself but also everything that is callable from JavaScript.

    Reasoning About Spectre

    To understand how Spectre works, it’s useful to think about how security-sensitive programming language operations (like any property access in JavaScript) get executed in JavaScriptCore on a modern processor. Most discussions about Spectre have involved bounds checks, so this section considers that case as well.

    var tmp = intArray[index];

    In this example, let’s assume that intArray is known to our JavaScript engine to be a reference to a Int32Array instance, but that we have not proved that index is in bounds of intArray.length. The compiler will have to emit a bounds check when it translates this high-level JavaScript operation into a lower-level form:

    if (((unsigned) index) >= ((unsigned) intArray->length))
    int tmp = intArray->vector[index];

    Compiling this on x86 CPUs results in the following instructions:

    mov 0x10(%rsi), %rdx     ; %rsi has intArray. This loads
                             ; intArray->vector.
    cmp 0x18(%rsi), %ecx     ; %ecx has the index. This compares
                             ; the index to intArray->length.
    jae Lfail                ; Branch to Lfail if
                             ; index >= intArray->length according
                             ; to unsigned comparison.
    mov (%rdx,%rcx,4), %ecx  ; Load intArray->vector[index].

    Modern CPUs are able to execute the bounds check branch (jae) and the subsequent load (mov (%rdx,%rcx,4), %ecx) in parallel. This is possible because:

    • Modern CPUs profile branches. In this case, they will observe that the branch always falls through. This is called branch prediction.
    • Modern CPUs can roll back execution. The load after the branch can execute before the CPU verifies that the branch actually did fall through. If the branch turns out to be taken instead, the CPU can undo everything that happened between when the branch was encountered and when it finally got verified. This is called speculative execution.

    Spectre is an attack that exploits information leaks from speculative execution. Consider this code:

    var tmp = intArray[index];
    otherArray[(tmp & 1) * 128];

    The CPU has the ability to initiate loads from main memory into L1 (the CPU’s level 1 memory cache, which is the fastest and smallest) while executing speculatively. As a performance optimization, the CPU does not undo fetches into L1 when rolling back speculative execution. This leads to a timing-based information leak: in this code, whether the CPU loads otherArray[0] or otherArray[128] depends on tmp & 1, and it’s possible to later determine which the CPU loaded speculatively by timing the speed of access to otherArray[0] and otherArray[128].

    The example so far involved controlling a bounds checking branch. This is a particularly effective Spectre attack because index behaves like a pointer that can be used to read ~16GB of memory above intArray->vector. But Spectre could theoretically involve any branch that enforces security properties, like the branches used for type checks in JavaScriptCore.

    To summarize:

    1. Spectre requires high fidelity timing so that the difference between L1 latency and main memory latency can be observed.
    2. Spectre lets attackers control branches. Speculative execution executes branches according to past history, and the attacker can control this history. Therefore, the attacker controls what branches do during speculative execution.
    3. Spectre is a race between the branch verifier and the initiation of the information-leaking load (what we wrote as otherArray[(tmp & 1) * 128] above). The attacker knows if they won the race (one of the two otherArray cache lines will be in L1), so the attack works so long as the attacker’s chance of winning is not zero.

    Mitigating Spectre

    WebKit’s response to Spectre is a two-tiered defense:

    1. WebKit has disabled SharedArrayBuffer and reduced timer precision.
    2. WebKit is transitioning to using branchless security checking in addition to branch-based security checking.

    Some of these changes shipped in the Jan 8 updates and more such changes are continuing to land in WebKit. The remainder of this document covers our mitigations in detail.

    Reducing Timer Precision

    We are reducing timer precision in WebKit. These changes have landed in trunk as of r226495 and they shipped in the Jan 8 updates.

    • Timer precision from and other sources is reduced to 1ms (r226495).
    • We have disabled SharedArrayBuffer, since it can be used to create a high-resolution timer (r226386).

    Our long-term plan is to make Spectre impossible even in the presence of high fidelity timing; further work is needed to re-enable this path.

    Branchless Security Checks

    Since learning about Spectre, we have been researching how to do security checks without relying on branches. We have begun making the transition to this new style of security checks and we shipped the first branchless checks in the Jan 8 updates.

    Index Masking

    The simplest example of a branchless security check is masking the index of an array access:

    int tmp = intArray->vector[index & intArray->mask];

    Modern CPUs do not speculate on bit masking. If the mask is picked to fit the array length, this mitigation ensures that even with Spectre, an attacker cannot read out-of-bounds of the array.

    We have implemented index masking for:

    1. Typed arrays (r226461),
    2. WebAssembly memories (r226461, mostly via shared code with typed arrays),
    3. Strings (r226068),
    4. WTF::Vector (r226068), and
    5. Plain JavaScript arrays (r225913).

    Changes (1-4) shipped in the Jan 8 updates. (5) landed in WebKit but has not yet shipped.

    Index masking is not yet a complete fix for out-of-bounds access. Our current index masking mitigations use a mask that is computed by rounding up the length to the next power of two (and subtracting one). This still allows out-of-bounds reads, just not to arbitrary memory.

    Our current testing indicates that index masking has no measurable impact on the Speedometer and ARES-6 tests and an impact of less than 2.5% on the JetStream benchmark.

    Pointer Poisoning

    Index masking is easy to apply for array accesses, but many security check branches have to do with object type, not array bounds. Pointer poisoning is a technique that can be used to make any type check secure under Spectre by changing the shape of the object subject to the check.

    Poisoning a pointer just means performing some reversible math on it that will make access attempts fail unless the pointer is unpoisoned. In WebKit, poisoning involves xoring a value that is sure to have at least one bit set in high positions so that accesses that do not unpoison are very likely to hit unmapped memory. WebKit picks poison values using a compile-time random number generator with lots of subtle rules, but to understand the approach, just consider 1 << 40 as a poison value. Adding one terabyte to a valid pointer is sure to result in an unmapped pointer in WebKit’s memory layout on macOS and iOS, and probably on other operating systems, too. Many possible poison values exist that would have this effect.

    Poisoning becomes most powerful when each static declaration of a pointer field has a unique poison value, and the poison values differ in the high bits so that unpoisoning with the wrong value results in an unmapped pointer.

    As an example of how to apply pointer poisoning as a branchless type check, consider some class Foo that belongs to a hierarchy of classes that participate in dynamic downcasts based on some checks:

    class Foo : public Base {
        int m_x;
        Bar* m_y;

    In order to make this class’s type checks sound under Spectre, we can simply move Foo’s fields out into a data struct pointed to by a uniquely poisoned pointer:

    class Foo : public Base {
        struct Data {
            int x;
            Bar* y;
        ConstExprPoisoned<FooDataKey, Data> m_data;

    Where FooDataKey is a key unique to Foo, based on which ConstExprPoisoned<> will compute a random poison value at compile time. If all classes in this hierarchy use a pointer poisoned indirection to protect their fields then this suffices as a branchless type check for all accesses to these types. In addition to being a great Spectre mitigation, this is also a useful remote code execution mitigation, since it makes it harder to do any kind of type confusion.

    Pointer poisoning sometimes does not require any extra indirections. JavaScriptCore has tons of data structures that roughly fit this pattern:

    struct Thingy {
        Type type;
        void* data; // The shape of this depends on `type`.

    Any such data structure’s type checks can be made branchless by poisoning the data pointer according to a poison value that depends on type.

    We have begun converting WebKit’s object models to use pointer poisoning (r225363, rr225437, r225632, r225659, r225697, r225857, r226015, r226247, r226344, r226485, r226530), and some of the initial pointer poisoning work is shipping in the Jan 8 updates (specifically, r225363r225857). So far, we have not observed any performance regressions from using pointer poisoning.

    Mitigating Meltdown

    Meltdown allows userland code to read kernel memory. WebKit is indirectly affected by Meltdown because a Meltdown attack could be initiated using any kind of code execution, including JavaScript. However, the memory accesses used to perform Meltdown would be a violation of WebKit’s security model. Therefore, JavaScript-based Meltdown attacks must first get around WebKit’s security checks such as by using a Spectre attack.

    If Meltdown has been mitigated by operating system changes, then even if WebKit lacked any Spectre mitigations, it would not be possible to mount a Meltdown attack via WebKit. Any future Spectre mitigations will make it even less likely that WebKit could be used for a Meltdown attack, since the Spectre stage of that attack will be harder.

    Recommendations For App Developers

    Spectre means that secrets in the same address space as untrusted JavaScript are more vulnerable than ever before. Based on this, we recommend:

    • Switch to the Modern WebKit API if you have not done so already. This protects your app by running untrusted JavaScript in another process.
    • Avoid exposing sources of high-precision timing to untrusted JavaScript or WebAssembly.


    Spectre and Meltdown are a new class of security issues that apply to modern processors and the software that runs on them. WebKit is affected by both issues because WebKit allows untrusted code to run on users’ processors. In response to these new issues, we have implemented mitigations to defend against Spectre (and Meltdown attacks launched using Spectre via the browser). The first of these mitigations have shipped in the Jan 8 updates (iOS 11.2.2, High Sierra 10.13.2 supplemental update, and Safari 11.0.2 reissue). Stay tuned for more WebKit Spectre fixes!

    By Filip Pizlo at January 09, 2018 12:49 AM