Add-ons/Thunderbird and SeaMonkey Add-ons FAQ

Where can I find add-ons to install?

Add-ons for Firefox and Firefox for Android can be found at https://addons.mozilla.org (also known as AMO).

Add-ons for Thunderbird and SeaMonkey can be found at https://addons.thunderbird.net.

Why is there a separate site for Thunderbird and SeaMonkey add-ons?

The Firefox add-on development platform was migrated in 2017 to a new technology called WebExtensions. This makes it easy to create powerful cross-browser add-ons using web technologies. Throughout 2018, all legacy add-ons and legacy features on AMO are being phased out.

Given that Thunderbird and SeaMonkey still use legacy add-on technology, it was decided it would be easier for the add-on websites to split, so AMO can do away with legacy features and continue its development.

Who runs the Thunderbird and SeaMonkey add-ons site?

The site is managed by the Thunderbird Council and runs on Mozilla infrastructure. It runs on a forked version of the AMO code, and the Mozilla Add-ons Team are working with the Thunderbird Council to make the transition as smooth as possible.

How does this affect add-on users on Thunderbird and SeaMonkey?

This shouldn’t affect users. All AMO URLs pointing to Thunderbird or SeaMonkey add-ons should redirect to the new site. Add-on update requests should also be redirected. New versions of Thunderbird and SeaMonkey should point directly to the new site, so the redirects are eventually unnecessary.

I’m a developer. Where can I find my add-ons?

If your add-ons are compatible with Firefox or Firefox for Android, they can be found on AMO. If they are compatible with Thunderbird or SeaMonkey, they can be found on https://addons.thunderbird.net. You should be able to log in using the same credentials as on AMO.

Since add-ons can support both Firefox and Thunderbird, or Firefox and SeaMonkey (or all of them), an add-on can be on both sites. The websites are independent, so changes done on one doesn’t reflect on the other.

How can I opt out of this process?

If you don’t want your add-ons on either site, you can go to your listing management page and either disable or delete your add-on. Note that if your add-on is on both sites, you might need to do this twice.

Where can I ask more questions about this?

You can post a message on our community forum or email amo-admins AT mozilla DOT com for additional information.