Today marks the release of Firefox 74 and as we announced last fall, developers will no longer be able to install extensions without the user taking an action. This installation method was typically done through application installers, and is commonly referred to as “sideloading.”
If you are the developer of an extension that installs itself via sideloading, please make sure that your users can install the extension from your own website or from addons.mozilla.org (AMO).
We heard several questions about how the end of sideloading support affects users and developers, so we wanted to clarify what to expect from this change:
- Starting with Firefox 74, users will need to take explicit action to install the extensions they want, and will be able to remove previously sideloaded extensions when they want to.
- Previously installed sideloaded extensions will not be uninstalled for users when they update to Firefox 74. If a user no longer wants an extension that was sideloaded, they must uninstall the extension themselves.
- Firefox will prevent new extensions from being sideloaded.
- Developers will be able to push updates to extensions that had previously been sideloaded. (If you are the developer of a sideloaded extension and you are now distributing your extension through your website or AMO, please note that you will need to update both the sideloaded .xpi and the distributed .xpi; updating one will not update the other.)
Enterprise administrators and people who distribute their own builds of Firefox (such as some Linux and Selenium distributions) will be able to continue to deploy extensions to users. Enterprise administrators can do this via policies. Additionally, Firefox Extended Support Release (ESR) will continue to support sideloading as an extension installation method.
We will continue to support self-distributed extensions. This means that developers aren’t required to list their extensions on AMO and users can install extensions from sites other than AMO. Developers just won’t be able to install extensions without the user taking an action. Users will also continue being able to manually install extensions.
We hope this helps clear up any confusion from our last post. If you’re a user who has had difficulty uninstalling sideloaded extensions in the past, we hope that you will find it much easier to remove unwanted extensions with this update.