Firefox development has recently moved to a rapid release cycle to bring new features and security, stability, and other bug fixes to hundreds of millions of users much faster than we have previously. In order to support this exciting new release schedule, a lot has to change, and one of the biggest areas impacted is add-on compatibility.

With past Firefox releases, add-ons were not marked as compatible with a new version until the developer manually tested and updated their add-on to support it. This process took months to get compatibility to an acceptable level and only worked because of the infrequency of Firefox releases. Our proposed plan for compatibility going forward assumes add-ons are compatible unless we find evidence that they aren’t.