Cross-posted from the Add-ons Blog
Mozilla will stop supporting Firefox Extended Support Release (ESR) 52, the final release that is compatible with legacy add-ons, on September 5, 2018.
As no supported versions of Firefox will be compatible with legacy add-ons after this date, we will start the process of disabling legacy add-on versions on addons.mozilla.org (AMO) in September. On September 6, 2018, submissions for new legacy add-on versions will be disabled. All legacy add-on versions will be disabled in early October, 2018. Once this happens, users will no longer be able to find your extension on AMO. For more information about how
After legacy add-ons are disabled, developers will still be able to port their extensions to the WebExtensions APIs. Once a new version is submitted to AMO, users who have installed the legacy version will automatically receive the update and the add-on’s listing will appear in the gallery.
For more information about porting legacy extensions to the WebExtensions API is available on MDN. We encourage legacy add-on developers to visit our wiki for more information about upcoming development work and ways to get in touch with our team for help.