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Microsoft Edge 154 web platform release notes (Sep. 2026)

The following are the new web platform features and updates in Microsoft Edge 154, which releases on Sep. 24, 2026.

To stay up-to-date and get the latest web platform features, download a preview channel of Microsoft Edge (Beta, Dev, or Canary); go to Become a Microsoft Edge Insider.

Detailed contents:

Microsoft Edge DevTools

See What's new in Microsoft Edge DevTools.

WebView2

See Release notes for WebView2.

CSS features

The following new Cascading Style Sheets (CSS) features are included in Microsoft Edge.

scroll-marker-group modes

The scroll-marker-group property now supports two modes: links and tabs.

  • links: The generated ::scroll-marker-group functions like a navigation list. This is the default mode.

    This mode is designed to mimic standard navigation landmarks that are combined with fragment anchors.

    The ::scroll-marker-group gets the navigation role and the ::scroll-marker elements get the link role, matching the <nav><a> structural pattern.

    All ::scroll-marker elements become sequential tab stops and, when activated, set the sequential focus navigation starting point to the target element, losing its own focus. This matches the behavior of clicking a <a href="#target"> link.

  • tabs: The generated ::scroll-marker-group functions like a tablist.

    This mode is designed to replicate the tabs pattern.

    The ::scroll-marker-group gets the tablist role, ::scroll-marker elements get tab roles, and their originating elements get the tabpanel role.

    To mimic the behavior of a tab panel, pressing the Tab key from the active marker moves focus directly into the active tabpanel content. Content from inactive tabs is explicitly hidden from the accessibility tree.

See also:

text-decoration-skip-spaces

The text-decoration-skip-spaces CSS property controls whether text decoration lines (such as underlines, overlines, or line-throughs) skip over white space characters.

This allows you to prevent decoration lines from being drawn on white space characters, to get more visually appealing results.

See also:

text-decoration-inset

The text-decoration-inset CSS property controls how far underlines, overlines, and line-through decorations are inset from or extended beyond the edges of the decorated text.

The text-decoration-inset CSS property supports the following:

  • auto.
  • Length values.
  • Percentage values.
  • Single and double-value syntaxes for setting the start and end offsets.

This lets you adjust decoration spacing and create reveal effects with native text decorations instead of background gradients or additional elements.

See also:

  • text-decoration-inset CSS property at MDN. This lets you adjust decoration spacing and create reveal effects with native text decorations, instead of background gradients or additional elements.

FontFace width attribute and font-width descriptor

The width attribute in the FontFace API and the font-width property in @font-face descriptors are now aliases for the stretch attribute and font-stretch property.

This aligns Microsoft Edge with the updated CSS Font Loading and CSS Fonts 4 specifications.

You can now inspect or initialize font face widths by using the FontFace.width property and the font-width CSS property.

See also:

Expose CSSStyleValue hierarchy to Worker contexts

The following constructors are now exposed in worker global scopes, in addition to window and worklet scopes:

  • CSSKeywordValue
  • CSSNumericValue
  • CSSStyleValue
  • CSSUnitValue
  • CSSUnparsedValue

These constructors are part of the CSS Typed Object Model specification.

This makes Microsoft Edge, and Chromium, compatible with Firefox and Safari.

See also:

HTML features

The following new HTML features are included in Microsoft Edge.

Responsively-sized <iframe>

The frame-sizing CSS property opts an <iframe> element into responsive sizing.

When responsively sized, the <iframe> element is sized in the parent document to the iframe document's size, so that scrollbars in the iframe are avoided.

See also:

Light dismiss improvements for popovers and dialogs

Light dismiss is the behavior where clicking outside of a popover or dialog closes it.

The light dismiss behavior for popovers and dialogs has been improved in Microsoft Edge 154. The following actions no longer trigger light dismiss:

  • Scrolling gestures on touch screens
  • Right-clicks

See also:

Web APIs

The following new Web API features are included in Microsoft Edge.

Options argument in the WebSocket constructor

The WebSocket constructor now accepts an option object as its second argument, for passing additional options to the WebSocket connection. This is an extension of the existing constructor signature, which previously only accepted a string for specifying subprotocols.

Specifying a subprotocol can now be written in either of the two following ways:

// Using the existing string argument for subprotocols.
const socket = new WebSocket("wss://example.com:8080", "soap");

// Using the new option bag argument for subprotocols.
const socket = new WebSocket("wss://example.com:8080", { protocols: "soap" });

See also:

targetAddressSpace option for WebSockets

Use the targetAddressSpace option, when calling the WebSocket constructor, to specify that a WebSocket connection to a public hostname should be treated as going to a "local" or "loopback" destination.

For example, a public website that connects to a local server can use a hostname to avoid needing manual configuration of the exact private IP address to use, as follows:

const ws = new WebSocket("ws://local-server.example", { targetAddressSpace: "local"});

This matches similar support on the Fetch API.

A common use case is bypassing mixed-content restrictions when connecting to local servers that cannot yet support HTTPS.

The user must grant the site the permission to access the local network.

See also:

New Web Cryptography algorithms

The Web Cryptography API now supports the following new cryptographic algorithms:

  • Post-quantum cryptography
  • Common symmetric AEAD

This gives you access to browser-provided implementations of common quantum-resistant cryptographic algorithms standardized by NIST:

  • ML-KEM - 768, 1024
  • ML-DSA - 44, 65, 87
  • ChaCha20-Poly1305
  • X-Wing

See also:

CORS enforcement for the Background Fetch API

The Background Fetch API now enforces Cross-Origin Resource Sharing (CORS).

This ensures that Background Fetch requests are subject to the same security policies, such as Local Network Access checks. This prevents sites from bypassing CORS (and other security policy checks) by using Background Fetch instead of regular Fetch.

See also:

Local Network Access restrictions for Background Fetch

The Background Fetch API now requires that the service worker's origin has the necessary Local Network Access permission in order to send requests to local or loopback servers.

This aligns the Background Fetch API with the Fetch API. This prevents sites from bypassing Local Network Access checks by using the Background Fetch API.

See also:

Fetch API: Forward reason from AbortController to fetch Response

The abort reason of an AbortController instance is now provided to the methods of the Response object and its ReadableStream, rather than just to the fetch promise.

See also:

Iterator.includes

JavaScript iterators now support the includes() method, letting you ask whether an iterator yields a given value.

This method is analogue to the includes() method on Array objects.

See also:

Origin trials

The following are origin trials for new experimental APIs that are available in Microsoft Edge.

Origin trials let you try experimental APIs on your own live website for a limited time. To learn more about origin trials, see Use origin trials in Microsoft Edge.

For the full list of available origin trials, see Microsoft Edge Origin Trials.

Name Description Register
Enhanced Canvas TextMetrics Expands the TextMetrics Canvas API, adding selection rectangles, bounding-box queries, and glyph-cluster operations. Register
Container Timing Monitors when an annotated DOM container is displayed and has finished its initial paint. Register
Separate style and layout durations in the Long Animation Frame API Adds styleDuration, forcedStyleDuration, layoutDuration, and forcedLayoutDuration properties, for deeper CSS performance analysis. Register
<install> HTML element Declaratively install other websites as web apps by using the <install> element. Register
Declarative CSS Module Scripts Shares declarative stylesheets with shadow roots, including declarative shadow roots, by using inline style modules. Register
Digital Credentials API - Issuance Support Triggers issuance of user credentials from a credential issuer server to a digital wallet application. Register
prerender_until_script Speculation Rules API action A Speculation Rules API action that prerenders a page, but switches to prefetching when a script executes. Register
Control viewport heuristics in Speculation Rules API Lets you control the viewport heuristics that are used by speculation rules, to determine if different heuristics parameters give you better results than the default ones. Register
Speculative Load measurement performance.speculations exposes data about used and unused preloads, prefetches, and prerenders. This helps you measure the effectiveness of speculative loading strategies and optimize performance-versus-cost tradeoffs. Register
PrefetchAndPrerenderActivationBeacon Allows Edge to reliably report an activation beacon when a prefetch or prerendered page is activated. Register
HTML in canvas Enables rendering HTML in a canvas by using new drawing methods and the paint event. Register
Autofill Event Detects when browser autofill updates form controls, for adapting custom UI and validation. Register
WebAssembly Custom Descriptors V2 Stores data that's associated with source-level types more efficiently, in custom descriptor objects. Register
WebMCP Enables your site to register tools for an in-browser agent to complete tasks on behalf of a user. Register
Email Verification Protocol Enables websites to verify email ownership by using cryptographic tokens that are issued by email providers. This reduces reliance on email one-time passcodes (OTPs), and streamlines sign-up, sign-in, and recovery flows. Register
WebRTC Data Channel: SCTP Negotiation Acceleration Protocol (SNAP) SNAP reduces WebRTC data channel startup latency by embedding SCTP connection setup parameters in the SDP offer/answer exchange. Because WebRTC already uses DTLS to establish a secure channel, the separate SCTP handshake can be avoided, saving up to two network round trips and enabling faster data channel establishment. Register
WebRTC Diagnostic Logging API Collects internal diagnostic logs for WebRTC-related operations. Register
Gamepad raw input event Instead of relying on frequent polling via navigator.getGamepads(), webpages can listen for gamepadrawinputchanged events. These events are fired whenever changes are detected between input frames from the same device. Register
Prerendering cross-origin iframes Prerenders cross-origin iframes via an opt-in response header, instead of delaying them until page activation. Register
Prompt API sampling parameters The topK and temperature sampling parameters let you optimize model behavior per language-model session. Register
JS Self-Profiling Markers Extends the JS Self-Profiling API with sample markers such as script, gc, style, layout, and paint. These markers identify the activity that the browser was doing at capture time. Register
Declarative Performance Observer API The Declarative Performance Observer API uses HTTP response headers to prove a reliable browser-managed telemetry system that reports performance metrics for the site, from navigation initiation to page termination. Register

Note

Portions of this page are modifications based on work created and shared by Chromium.org and used according to terms described in the Creative Commons Attribution 4.0 International License.

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