Manifest V3 Updates

Greetings add-on developers! We wanted to provide an update on some exciting engineering work planned for the next few Firefox releases in support of Manifest V3. The team continues to implement API changes that were previously defined in agreement with other browser vendors that participate in the WECG, ahead of Chrome’s MV2 deprecation. Another top area of focus has been around addressing some developer and end user friction related to MV3 host permissions.

The table below details some MV3 changes that are going to be available in the Firefox release channel soon.

Version	Manifest V3 engineering updates	Nightly	Beta	Release
126	Chrome extension porting API enhancements: The “webRequestAuthProvider” permission is now supported to provide compatibility with Chrome for requesting permission for webRequest.onAuthRequired in Manifest V3 The options_page manifest key is provided as an alias of the options_ui key to offer better extension compatibility with Chrome	3/18	4/15	5/14
127	Updating MV3 host permissions on both desktop and mobile.	4/15	5/13	6/11
128	Implementing the UI necessary to control optional permissions and supporting host permissions on Android that landed in 127.	5/13	6/10	7/9

The Chrome extension porting API work that will land beginning in 126 will help ensure a higher level of compatibility and reduce friction for add-on developers supporting multiple browsers.

Beginning with Firefox 127, users will be prompted to grant MV3 host permissions as part of the install flow (similar to MV2 extensions). We’re excited to deliver this work as based on feedback from Firefox users and extension developers, this has been a major hurdle for MV3 extensions in Firefox.

However, unlike the host permission granted at install time for MV2 extensions, MV3 host permissions can still be revoked by the user at any time from the about:addons page on Firefox Desktop. Given that, MV3 extensions should still leverage the permissions API to ensure that the permissions required are already granted.

Lastly, in Firefox for Android 128, the Add-ons Manager will include a new permissions UI as shown below — this new UI will allow users to do the same as above on Firefox for Android with regards to host permissions, while also granting or revoking other optional permissions on MV2 and MV3 extensions.

                             

We also wanted to take this opportunity to address a couple common questions we’ve been seeing in the community, specifically around the webRequest API and MV2:

1. The webRequest API is not on a deprecation path in Firefox
2. Mozilla has no current plans to deprecate MV2 as mentioned in our previous MV3 update

For more information on adopting MV3, please see our migration guide. Another great resource is the FOSDEM presentation a couple Mozilla engineers delivered recently, Firefox, Android, and Cross-browser WebExtensions in 2024.

If you have questions or feedback on our Manifest V3 plans we would love to hear from you in the comments section below or if you prefer, drop us an email.