Mozilla is dropping support for sideloaded extensions in Firefox

Mozilla is clamping down on browser add-ons in Firefox, and has announced that it is discontinuing sideloaded extensions in the browser.

The reason given for dropping support is that Mozilla believes that sideloaded extensions cause problems for users, and also that they do not offer users enough control. The company has set out details of the timetable for introducing the new policy.

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Announcing the upcoming changes in a blog post, Mozilla says: "Sideloaded extensions frequently cause issues for users since they did not explicitly choose to install them and are unable to remove them from the Add-ons Manager. This mechanism has also been employed in the past to install malware into Firefox. To give users more control over their extensions, support for sideloaded extensions will be discontinued".

The change will be introduced in the pre-release version of Firefox 73 which is scheduled to arrive next month. Mozilla explains:

During the release cycle for Firefox version 73, which goes into pre-release channels on December 3, 2019 and into release on February 11, 2020, Firefox will continue to read sideloaded files, but they will be copied over to the user's individual profile and installed as regular add-ons. Sideloading will stop being supported in Firefox version 74, which will be released on March 10, 2020. The transitional stage in Firefox 73 will ensure that no installed add-ons will be lost, and end users will gain the ability to remove them if they chose to.

The change will not stop people from self-distributing their own extensions, but distribution must be carried out through either the official add-ons repository, or a self-owned web property with an update URL for users to obtain patches and updates. Mozilla also stresses that all extensions must comply with its Add-on Policies and Developer Agreement.