A few days ago, Mozilla has made an official announcement saying that on November 14, 2017 it will release the Firefox 57, which will actually be the first version of the browser that will stop supporting legacy Firefox add-ons.
That being said, Firefox 57 will only support new add-ons that are written on top of the newer WebExtensions SDK. Unfortunately, all legacy Firefox add-ons that have been written on the old XUL-based add-ons SDK will not function at all.
Old Legacy Add-ons Will Still Exist
The good news is that Mozilla has confirmed that it will continue allowing developers to upload and list legacy Firefox add-ons on its add-ons portal. However, these add-ons will only show up for the users that will have Firefox version 56 or below installed on their computers.
We have to mention that the changes are already being rolled on Firefox 57 (currently Firefox’s Nightly edition) and AMO. Keep in mind that the upcoming Firefox 57 is the end of a two-year project that was started back in August 2015, when Mozilla has announced the new WebExtensions API that would eventually replace the older Add-Ons SDK.
The new extension is compatible with the universal WebExtensions SDK implemented in Chromium and related browsers such as Opera, Chrome, Vivaldi or Brave.
20% of all Firefox Add-ons Are WebExtensions-ready
As most of you already know, Firefox comes with a large amount of legacy add-ons. In fact, this has always been one of the main reasons why it became some popular. However, when Mozilla has announced the new WebExtensions SDK, everyone has feared about the old legacy add-ons and thought that the developers of these add-ons will not update them to the newer WebExtensions API.
The good news is that many developers are already trying to get their legacy add-ons to the newer WebExtensions API. In fact, there are already 20% of the add-ons that are WebExtensions-ready and let’s not forget that there are still three months until the new Firefox 57 version will be officially launched.