Unless otherwise noted, changes described below apply to the newest Chrome beta channel release for Android, Chrome OS, Linux, macOS, and Windows. Learn more about the features listed here through the provided links or from the list on ChromeStatus.com. Chrome 96 is beta as of October 21, 2021.

Preparing for a Three Digit Version Number

Next year, Chrome will release version 100. This will add a digit to the version number reported in Chrome's user agent string. To help site owners test for the new string, Chrome 96 introduces a runtime flag that causes Chrome to return '100' in its user agent string. This new flag called chrome://flags/#force-major-version-to-100 is available from Chrome 96 onward.

Origin Trials

This version of Chrome introduces the origin trials described below. Origin trials allow you to try new features and give feedback on usability, practicality, and effectiveness to the web standards community. To register for any of the origin trials currently supported in Chrome, including the ones described below, visit the Chrome Origin Trials dashboard. To learn more about origin trials in Chrome, visit the Origin Trials Guide for Web Developers. Microsoft Edge runs its own origin trials separate from Chrome. To learn more, see the Microsoft Edge Origin Trials Developer Console.

New Origin Trials

Conditional Focus

Applications that capture other windows or tabs currently have no way to control whether the calling item or the captured item gets focus. (Think of a presentation feature in a video conference app.) Chrome 96 makes this possible with a subclass of MediaStreamTrack called FocusableMediaStreamTrack, which supports a new focus() method. Consider the following code:

stream = await navigator.mediaDevices.getDisplayMedia();
let [track] = stream.getVideoTracks();

Where formerly, getVideoTracks() would return an array of MediaStreamTrack objects, it now returns FocusableMediaStreamTrack objects. (Note that this is expected to change to BrowserCaptureMediaStreamTrack in Chrome 97. At the time of this writing, Canary already does this.)

To determine which display media gets focus, the next line of this code would call track.focus() with either "focus-captured-surface" to focus the newly captured window or tab, or with "no-focus-change" to keep the focus with the calling window. On Chrome 96 or later, you can step through our demo code to see this in action.

Priority Hints

Priority Hints introduces a developer-set "importance" attribute to influence the computed priority of a resource. Supported importance values are "auto", "low", and "high". Priority Hints indicate a resource's relative importance to the browser, allowing more control over the order resources are loaded. Many factors influence a resource's priority in browsers including type, visibility, and preload status of a resource.

Other Features in this Release

Allow Simple Range Header Values Without Preflight

Requests with simple range headers can now be sent without a preflight request. CORS requests can use the Range header in limited ways (only one valid range) without triggering a preflight request.

Back-forward Cache on Desktop

The back-forward cache stores pages to allow for instant navigations to previously-visited pages after cross-site navigations.

Cross-Origin-Embedder-Policy: credentialless

Cross-Origin-Embedder-Policy has a new credentialless option that causes cross-origin no-cors requests to omit credentials (cookies, client certificates, etc.). Similarly to COEP:require-corp, it can enable cross-origin isolation.

Sites that want to continue using SharedArrayBuffer must opt-in to cross-origin isolation. Doing so using COEP: require-corp is difficult to deploy at scale and requires all subresources to explicitly opt-in. This is fine for some sites, but creates dependency problems for sites that gather content from users (Google Earth, social media generally, forums, etc).

CSS

:autofill Pseudo Class

The new autofill pseudo class enables styling autofilled form elements. This is a standardization of the :-webkit-autofill pseudo class which is already supported in WebKit. Firefox supports the standard version.

Disable Propagation of Body Style to Viewport when Contained

Some properties like writing-mode, direction, and backgrounds are propagated from body to the viewport. To avoid infinite loops for CSS Container Queries, the spec and implementation were changed to not propagate those properties when containment is applied to HTML or BODY.

font-synthesis Property

The font-synthesis CSS property controls whether user agents are allowed to synthesize oblique, bold, and small-caps font faces when a font family lacks faces.

EME MediaKeySession Closed Reason

The MediaKeySession.closed property now uses an enum to indicate the reason the MediaKeySession object closed. The closed property returns a Promise that resolves when the session closes. Where previously, the Promise simply resolved, it now resolves with a string indicating the reason for closing. The returned string will be one of "internal-error", "closed-by-application", "release-acknowledged", "hardware-context-reset", or "resource-evicted".

HTTP to HTTPS Redirect for HTTPS DNS Records

Chrome will always connect to a website via HTTPS when an HTTPS record is available from the domain name service (DNS).

InteractionID in EventTiming

The PerformanceEventTiming interface now includes an attribute called interactiveID. This is a browser-generated ID that enables linking multiple PerformanceEventTiming entries when they correspond to the same user interaction. Developers can currently use the Event Timing API to gather performance data about events they care about. Unfortunately, it is hard to link events that correspond to the same user interaction. For instance, when a user taps, many events are generated, such as pointerdown, mousedown, pointerup, mouseup, and click.

New Media Query: prefers-contrast

Chrome supports a new media query called 'prefers-contrast', which lets authors adapt web content to the user's contrast preference as set in the operating system (specifically, increased contrast mode on macOS and high contrast mode on Windows). Valid options are 'more', 'less', 'custom', or 'no-preference'.

Unique id for Desktop PWAs

Web app manifests now support an optional id field that globally identifies a web app. When the id field is not present, a PWA falls back to start_url. This field is currently only supported on desktop.

URL Protocol Handler Registration for PWAs

Enable web applications to register themselves as handlers of custom URL protocols/schemes using their installation manifest. Operating system applications often register themselves as protocol handlers to increase discoverability and usage. Web sites can already register to handle schemes via registerProtocolHandler(). The new feature takes this a step further by letting web apps be launched directly when a custom scheme link is invoked.

WebAssembly

Content Security Policy

Chrome has enhanced Content Security Policy to improve interoperability with WebAssembly. The wasm-unsafe-eval controls WebAssembly execution (with no effect on JavaScript execution). Additionally, the script-src policies now include WebAssembly.

Reference Types

WebAssembly modules can now hold references to JavaScript and DOM objects. Specifically, they can be passed as arguments, stored in local and global variables, and stored in WebAssembly.Table objects.

Deprecations and Removals

This version of Chrome introduces the deprecations and removals listed below. Visit ChromeStatus.com for lists of current deprecations and previous removals.

The "basic-card" Method of PaymentRequest API

The PaymentRequest API has deprecated the basic card payment method. Its usage is low and declining. It underperforms when compared to other payment methods in time-to-checkout and completion rate. Developers can switch to other payment methods as an alternative. Examples include Google Pay, Apple Pay, and Samsung Pay.

Removal timeline:

• Chrome 96: the basic-card method is deprecated in the Reporting API.
• Chrome 100: the basic-card method will be removed.

• is up to 8% more responsive on real pages,
• saves more than 1400 years of CPU time per day, and
• improves battery life by up to 0.5%

• 150% or more faster graphics rendering, and
• greater reliability, due to a 6x reduction in GPU driver crashes on problematic hardware

IntroductionRenderingNG is a long-term project to systematically improve Chrome performance as experienced by our users over time, while also anticipating future needs. This enables the web to stay fast even as the web becomes ever richer and more featureful.

RenderingNG

We began the journey more than 8 years ago, and I’m happy to report that in 2021, the core RenderingNG projects are coming to a conclusion. This not only makes the existing web super fast, but even better, it means Chrome is ready for the next generation of web content.

RenderingNG is comprised of three elements: performance, reliability and extensibility.

The pyramid of success

PerformanceLet’s start with performance.

GPU & multi-core

A great way Chrome can render content faster is to take advantage of the multi-core CPUs and advanced GPUs present in today’s devices. Multi-core means we can do multiple kinds of work in parallel. For example, Chrome parallelizes running JavaScript, scrolling a web page, decoding an image or video, and rastering new content that will be on-screen soon. GPUs enable even more parallelization by rastering every pixel on-screen, rather than one-at-a-time, yielding a large speedup.

Earlier generations of browsers were not built to natively support these technologies, because at the time GPUs and multi-core computers were not widespread. It turned out that bolting on highly parallel features was extremely challenging, requiring the team to re-architect the entire Chrome rendering pipeline over time. This re-architecture is RenderingNG.

Scaling up and scaling downTo avoid exhausting available resources and potentially diminishing the user experience of the web, browsers must be respectful of efficiency. They should not slow down your ability to interact with your computer or phone, or keep you from multitasking between the browser and other apps. Likewise, browsers also need to maximize battery life of your phone and laptop, and prevent the device itself from getting too hot (here’s looking at you, CPU cooling fans!). And finally, the browser must always be smooth and responsive to the user.

This means that the browser needs to be able to scale up and down its use of the GPU and multi-threading to balance multitasking, battery, and device temperature. As one example of scaling up, it’s important that scrolling happen in parallel with JavaScript on all devices; otherwise the browser will have poor user responsiveness. On the other hand, there are times when the browser must scale down because battery life may be considered more important than maximum use of GPU and CPU resources to make rendering faster.

It turns out to be challenging to be able to scale up and scale down seamlessly, and in a way that doesn’t break web content or make the browser unresponsive in key situations. RenderingNG applies novel technologies throughout the stack to make this work, including a complete rewrite of how compositing works, enabling the flexible use of GPU or CPU computations for arbitrary pieces of web pages, in order to pick the right fit for each web page and device.

Performance isolationThe third key technique is performance isolation. Performance isolation is what allows you to have a nice experience reading your email while music and video is playing in the background: your computer and operating system (OS) architecture makes sure that they all share the CPU fairly and smoothly. (This feature has been around for native apps for so long, we just take it for granted, but it wasn’t always that way!)

Browsers already have good isolation from other apps on your computer (thanks to the OS), but within a web page, it can be difficult to isolate all the pieces, such as iframes for ads and other embedded content, video and audio, animations, scrolling, JavaScript, and various other browser tasks. In earlier eras of the web, it was a huge achievement to simply make all these features work at all. Now the bar has been raised, and they need to fit together seamlessly in order to create a reliably fast user experience on the web.

RenderingNG’s architecture implements performance isolation for all of these features.

ReliabilityMost of our work has been focused on reliability of the user experience. This is especially true when rewriting the entire rendering stack of a web browser--a huge and potentially risky undertaking.

We did this with four key techniques:

• Comprehensive testing, such as a huge battery of Web Platform Tests,
• Measuring progress in reliability, through metrics that track performance & quality, and committed goals such as Compat2021,
• Listening to and acting on bug reports and feedback,
• Good software design patterns.

Compat2021 improvements over time

ExtensibilityFinally, we always have one eye toward what web apps will need now and in the future to unlock better and better experiences for users. These apps are always pushing at the boundary of what is possible to do well on the web, and sometimes beyond. When they go beyond what current web APIs or architectures were designed for, the web app may still work, but it’ll sometimes be slower and more cumbersome to use---and more taxing on your computer than necessary. We are filling these gaps with new APIs that allow web apps to continue doing all these things, but in a way that is much easier to implement performantly.

Extensibility has been part of the design of RenderingNG from the beginning, and is a big reason why the system is clean and modular.

Results

The first RenderingNG performance optimization shipped in 2015. Below we’ve highlighted a few of the many subsequent performance improvements since then.

CompositeAfterPaint: faster and more responsive on all pages [1]In the M94 release, we will ship CompositeAfterPaint, a new compositing subsystem that allows for arbitrary scaling up and down of GPU use for web app content. Even better, due to more efficient, purpose-built algorithms in this subsystem, CompositeAfterPaint will substantially improve:

• Scroll latency by up to 8%
• Responsiveness by up to 3%
• Peak rendering speed by up to 3%
• GPU memory use by more than 3%
• CPU time spent rendering and interacting with tabs, resulting in a savings of more than 1400 years of CPU time per day
• Battery life by up to 0.5%

GPU Raster: dramatically faster than before [2]When it shipped on Mac in 2016, GPU raster resulted in a 37% improvement on the overall MotionMark benchmark, and 150% on HTML categories. We subsequently brought similar wins to all other platforms and content types, concluding in 2020. In 2021 we shipped improvements focused on further GPU acceleration for 2D Canvas rendering, with up to a 1000% improvement in the Path rendering test, and a 130% improvement overall on the MotionMark 1.2 benchmark, as measured on an Apple M1 Mac.

 
Out-of-process Raster: much-improved reliability [1]Out-of-process raster shipped on Android in 2018. This reduced the crash rate for problematic GPU drivers by 6x, bringing reliability in line with other drivers.

Learn moreIf you’d like to learn more about RenderingNG, head over to the Chrome Developers Blog, where we are publishing a whole series about the project, with more to come over time.

Thanks for reading!

Posted by Chris Harrelson, Lead Rendering Software Engineer

[1] Data source: Real-world data anonymously aggregated from Chrome clients.
[2] Data source: MotionMark.