New to the web platform in November

Discover some of the interesting features that have landed in stable and beta web browsers during November 2025.

Rachel Andrew

Published: November 26, 2025

Stable browser releases

Firefox 145 and Safari 26.1 released to stable during November, this post takes a look at what that means for the web platform.

Safari 26.1

This release of Safari is mostly a release that fixes bugs and compatibility issues with existing features.

There's a couple of additions with support for relative units in SVG, and support for remembering the last successful position-try fallback in CSS anchor positioning to reduce layout jumps when styles change.

Atomics.waitAsync()

Firefox 145 now supports the Atomics.waitAsync() static method. This method allows synchronization of threads based upon the value in a shared memory location. It waits asynchronously for the value and returns an object representing the operation's result. With this release, it's now Baseline Newly available.

The ToggleEvent source property

Firefox also supports the source property of the ToggleEvent interface. If a popover is triggered to open or close by an HTML element such as a <button>, the event's source property will contain the element that triggered the popover.

The Integrity-Policy and Integrity-Policy-Report-Only HTTP headers

The Integrity-Policy and Integrity-Policy-Report-Only HTTP headers are supported in Firefox for script resources. These allow websites to enforce subresource integrity guarantees for scripts.

Beta browser releases

Beta browser versions give you a preview of things that will be in the next stable version of the browser. It's a great time to test new features, or removals, that could impact your site before the world gets that release. New betas this month are Firefox 146 and Safari 26.2.

Firefox 146 includes the CSS contrast-color() function and the display-p3-linear color space in <color>. Also included is the CSS @scope at-rule letting you select elements in specific DOM subtrees, which will become Baseline Newly available.

Safari 26.2 is shaping up to be a release full of new features for the browser. It includes the CSS random() function, along with the field-sizing property. hidden=until-found is also included, as are the command and commandfor attributes on buttons.