Site compatibility-impacting changes coming to Microsoft Edge

This article lists the schedule of changes for Microsoft Edge and the Chromium project. It also highlights any differences and high-impact changes which the Microsoft Edge team is tracking especially closely.

The web platform is a collection of technologies used for building webpages, including HTML, CSS, JavaScript, and many other open standards. The web platform constantly evolves to improve the user experience, security, and privacy. In some cases, these changes may affect the functionality of existing webpages.

For functionality and compatibility reasons, Microsoft Edge adopts nearly all of the Chromium project's changes to the web platform. However, Microsoft retains full control of the Microsoft Edge browser and may defer or reject changes. The Microsoft Edge team decides if the change benefits browser users.

For information about upcoming Chromium project web platform changes, see Chrome Platform Status Release timeline.

Check this article often as the Microsoft Edge team updates this article as thinking evolves, timelines solidify, and new changes are announced.

Differences from the Chromium schedule, and high-impact changes

This table lists:

  • Changes where the rollout schedule for Microsoft Edge differs from the upstream Chromium project.
  • High-impact changes which the Microsoft Edge team is tracking closely.
Change Stable channel Experimentation Additional information
Deprecate unload event Future release (TBD) Introduces a new Permission-Policy to allow creating unload event listeners. The default policy is allow, but the default policy will gradually be migrated to deny, such that unload handlers stop firing on pages, unless a page explicitly opts in to re-enable them. This change is happening in the Chromium project, on which Microsoft Edge is based. For more information, see Intent to Deprecate: Deprecate unload event.
Removal of cross-origin subframe JavaScript dialogs Future release (TBD) Removes window.alert, window.prompt, and window.confirm from cross-origin iframes. This change is happening in the Chromium project, on which Microsoft Edge is based. For more information, see Intent to Remove: Cross origin subframe JS Dialogs.
Removal of mutation events v127 Removes support for mutation events in Chromium. Use the MutationObserver API instead. See Intent to Deprecate: Mutation Events.
Added support for AVIF and AV1 file formats v121 Microsoft Edge now supports the AVIF and AV1 file formats, which offer better compression and higher quality images and videos. Users can enjoy faster loading times and better quality media on websites.
Ignore modifications to document.domain by default v119 The document.domain property historically could be set to relax the same-origin policy and allow subdomains from a site to interact. This behavior will be disabled by default such that setting the document.domain property will have no effect. For more information and workarounds, see Microsoft Edge will disable modifying document.domain.
New TLS server certificate verifier v111 (managed devices), v109 (unmanaged devices) No site compatibility impacts are anticipated. If you have uncommon TLS server certificate deployments, you should test in v109 to confirm there's no impact. For more information and testing guidance, see Changes to Microsoft Edge browser TLS server certificate verification.

Notation for browser versions

This article uses the following notation for browser release numbers.

Notation Description
v123 The feature or change ships in Microsoft Edge version 123.
v123 (Chrome+1) The feature or change ships in Microsoft Edge version 123, which is one release after the feature or change ships in Chrome version 122.
v123 (Chrome+2) The feature or change ships in Microsoft Edge version 123, which is two releases after the feature or change ships in Chrome version 121.
Beta v123 The feature or change ships in version 123 of the Beta preview channel of Microsoft Edge.
Dev v123 The feature or change ships in version 123 of the Dev preview channel of Microsoft Edge.
Canary v123 The feature or change ships in version 123 of the Canary preview channel of Microsoft Edge.