Experimental Chromium Web Platform Features

Allows callers to specify a `maxAge` when setting a cookie with the Cookie Store API. Cookie expiry time is already configurable using the `expires` attribute, but `maxAge` provides a more idiomatic option and aligns the Cookie Store API with the options provided by `document.cookie` and the `Set-Cookie` HTTP Header.

This change updates Chromium’s emoji rendering behavior in Forced Colors Mode. During computed-value resolution, emoji whose font-variant-emoji value computes to normal or unicode are rendered using their monochrome glyphs when available. Chromium will therefore suppress color emoji rendering, which ensures emojis fully participate in the Forced Colors Mode pipeline and respect system high-contrast colors. Behavior outside forced colors mode is unchanged.

This extends speculation rules to introduce a new action called prerender_until_script. It is designed as an intermediate option between the existing prefetch (which only fetches the main document) and prerender (which fully renders the page and runs all scripts). This new action will fetch and parse a page, discover and download its subresources like images and stylesheets, but will pause all script execution. When the user navigates to the page, it activates, and all the deferred scripts are then executed in order. This allows for a near-instant page load for content-heavy sites without the performance cost or side effects of running analytics or third-party scripts prematurely.

Context-aware media element(s), are a declarative, user-activated control for accessing the starting and interacting with media streams. This addresses the long-standing problem of permission prompts being triggered directly from JavaScript without a strong signal of user intent. By embedding a browser-controlled element in the page, the user's click provides a clear, intentional signal. This enables a much better prompt UX and, crucially, provides a simple recovery path for users who have previously denied the permission. Note: This feature was previously developed and tested in an Origin Trial as the more generic <permission> element. Based on feedback from developers and other browser vendors, it has evolved into capability-specific elements to provide a more tailored and powerful developer experience.

Add a CanvasToneMapping member to CanvasRenderingContext2DSettings, allowing a 2D context to specify tone mapping.

Add display-p3-linear CSS color space

Allows authors to style descendants of containers based on the most recent scrolling direction. Example: .scrolling-up { translate: 80px 0; transition: 0.4s translate; } html { container-type: scroll-state; } @container scroll-state(scrolled: top) { .scrolling-up { translate: 0 0; } }

This feature changes the attribution data (prevRect and currentRect) in the [LayoutShift API](https://wicg.github.io/layout-instability/) to be reported in CSS pixels instead of physical pixels. The current behavior is inconsistent with other layout-related APIs, which all use CSS pixels. This change improves consistency, simplifies usage for developers, and aligns with expected units in debugging and tooling.

Adds support for ping, hreflang, type, and referrerPolicy attributes on SVGAElement, aligning its behavior with HTMLAnchorElement for consistent link handling across HTML and SVG.

Trusted Types (https://developer.mozilla.org/en-US/docs/Web/API/Trusted_Types_API) was originally implemented and launched in Chromium in 2019, and has since found use in numerous websites. It has recently gained interest from other browser vendors. The Trusted Type spec was co-written as a "monkey patch" spec along with our original implementation. It now receives fresh attention as others are trying to implement the same spec. It has now been "upstreamed" into HTML + DOM (plus a bit of CSP). As part of that process, various inconsistencies are being identified and fixed. Some of these fixes may be developer observable. This intent is to update our implementation to match the spec, as it's upstreamed into HTML. Meanwhile, WebKit has launched their implementation of the updated Trusted Types spec, which gives us high confidence that this update is highly web compatible.

The ViewTransition automatically constructs a pseudo-element tree to display and animate participating elements in the transition. Per spec, this subtree is constructed when the view transition starts animating and is destroyed when the animations associated with all view transition pseudo-elements are in the finished state (or more precisely in a non-running non-paused state). This works for a vast majority of cases and provides a seamless experience for the developers. However, for more advanced cases, this is insufficient as there are times when developers want the view transition pseudo-tree to persist beyond the animation finish state. One example is tying view transitions with Scroll Driven Animations. When the animation is controlled by a scroll timeline, we don't want the subtree to be destroyed when the animations finish since scrolling back should still be able to animate the pseudo elements. In order to enable advanced uses of view transition, this intent adds a waitUntil() function on the ViewTransition object which takes a promise. This promise then delays destruction of the pseudo-tree until it is settled.

This Web Platform feature enables issuing websites (e.g., a university, government agency, or bank) to securely initiate the provisioning (issuance) process of digital credentials directly into a user's mobile wallet application. On Android, this capability leverages the Android IdentityCredential CredMan system (Credential Manager). On Desktop, it leverages cross-device approaches using the CTAP protocol similar to Digital Credentials presentation.

WebMCP is a proposal for a web API that enables web pages to provide agent-specific paths in their UI. With WebMCP, agent-service interaction takes place via app-controlled UI, providing a shared context available to app, agent, and user.

Adds an XRVisibilityMaskChange event that will provide a list of vertices and a list of indices to represent the mesh of the visible portion of the user's viewport. This data can then be used to confidently limit the amount of the viewport drawn to in order to improve performance. To better support this event, XRView's are also given unique identifiers to allow easier pairing with the associated masks. This is an extension to the core WebXR specification.

The HTMLElement.accessKeyLabel read-only property returns a human-readable string representing the actual keyboard shortcut assigned to the element by the browser, based on the user’s platform and browser. If no access key is assigned, it returns an empty string.

Ignore tree-scope when matching container-name for @container queries. Previously, container-name matching for container queries used tree-scoped names/references for matching, which meant the same name would not match if the @container rule and the container-type property were originating from different trees such that that container-type declaration came from an inner shadow tree. With this change container names match regardless of @container rule or container-type declaration origins.

Support of new CSS property `ruby-overhang` is added. The property accepts one of `auto` and `none` keywords, and controls overhang of ruby annotation text.

This feature introduces support for the font-language-override CSS property in Chromium. The property allows developers to override the system language used for OpenType glyph substitution by specifying a four-character language tag directly in CSS. This enables fine-grained typographic control, particularly useful for multilingual content or fonts with language-specific glyph variants.

Modulepreload and dynamic imports now correctly send the page’s referrer header when fetching scripts, aligning Chrome with the HTML specification.

Currently NavigationTransition has a "from" property, exposing the old URL of the navigation. Exposing "to" (a NavigationDestination) completes this. It is especially useful when using precommit handlers, as during precommit the current URL has not yet switched to the destination. Note that navigation.transition is only exposed for intercepted navigations - which means same-origin document-initiated navigations.

This feature supports applying width and height as presentation attributes on nested <svg> elements through both SVG markup and CSS. This dual approach provides even greater flexibility for developers, allowing them to manage and style SVG elements more efficiently within complex designs. With this feature the below two html will now have the same output: With CSS Properties for nested <svg> element: <svg width="100px" height="100px"> <svg style="width:50px;height:50px;"> <circle cx="50px" cy="50px" r="40px" fill="green" /> </svg> </svg> Without CSS Properties for nested <svg> element: <svg width="100px" height="100px"> <svg width="50px" height="50px"> <circle cx="50px" cy="50px" r="40px" fill="green" /> </svg> </svg>

These pseudo-classes match scroll markers that are, respectively, before or after the active marker (the one matching :target-current) within the same scroll marker group, as determined by flat tree order: * :target-before matches all scroll markers that precede the active marker in the flat tree order within the group. * :target-after matches all scroll markers that follow the active marker in the flat tree order within the group.

This proposal untangles ‘border-width’, ‘outline-width’, and ‘column-rule-width’ from their corresponding ‘*-style’ properties. Previously, if a ‘*-style’ property, such as ‘border-style’, was set to ‘none’ or ‘hidden’, the computed ‘*-width’, such as ‘border-width’, would resolve to ‘0px’, even if the width was explicitly set to ‘10px’. Following a resolution in the CSSWG [1], the computed values of ‘border-width’, ‘outline-width’, and ‘column-rule-width’ will now reflect their specified values, regardless of the associated style property's value. Similarly, the resolved values of ‘outline-width’, and ‘column-rule-width’ will now reflect their specified values, regardless of the associated style property's value. [1]: https://github.com/w3c/csswg-drafts/issues/11494#issuecomment-2675800489

View Transitions API allows developers to start visual transitions between different states. The primary SPA entry point to this is `startViewTransition()` which returns a transition object. This object contains several promises and functionality to track the transition progress, as well as allow manipulations such as skipping the transition or modifying its types. The proposal here is ergonomic in nature: instead of requiring that users store this object in some sort of way for easy access, provide a `document.activeViewTransition` property that represents this object, or null if there is no transition ongoing. Note this similarly applies to MPA transitions, where the object is only available via `pageswap` and `pagereveal` events. In this proposal `document.activeViewTransition` would be set to this object for the duration of the transition.

By using the size and multiple attributes, the select element can be rendered as an in-page listbox or a button with a popup. However, these modes are not consistently available across mobile and desktop chrome. Currently, in-page listbox rendering is not available on mobile, and button with popup is not available on desktop when the multiple attribute is present. This feature adds the listbox to mobile and adds a multi-select popup to desktop, and makes the opt-ins with the size and multiple attributes result in the same rendering mode across mobile and desktop. Here is a summary of the changes: - When the size attribute has a value greater than 1, in-page rendering will always be used. Previously, this was ignored on mobile. - When the multiple attribute is set with no size attribute, in-page rendering will be used. Previously, this was a popup instead of an in-page listbox on mobile. - When the multiple attribute is set with size=1, a popup will be used. Previously, this was an in-page listbox on desktop. By making this change, we are providing a foundation to bring customizable select to in-page rendering and multi-select. Customizable select currently only works for single-selects with a popup.

This feature introduces support for the download attribute on the SVGAElement interface in Chromium, aligning with the SVG 2 specification. The download attribute enables authors to specify that the target of an SVG hyperlink should be downloaded rather than navigated to, mirroring the behavior already supported in HTMLAnchorElement. This enhancement promotes interoperability across major browsers and ensures consistent behavior between HTML and SVG link elements, thereby improving developer experience and user expectations.

WebTransport Application Protocol Negotiation allows negotiation of the protocol used by the web application within the WebTransport handshake. A web application can specify a list of application protocols offered when constructing a WebTransport object, which are then conveyed to the server via HTTP headers; if the server picks one of those protocols, it can indicate that within response headers, and that reply is available within the WebTransport object.