New site for Thunderbird add-ons

When Firefox Quantum (version 57) launched in November 2017, it exclusively supported add-ons built using WebExtensions APIs. (AMO) has followed a parallel development path to Firefox and will soon only support WebExtensions-based add-ons.

As Thunderbird and SeaMonkey do not plan to fully switch to the WebExtensions API in the near future, the Thunderbird Council has agreed to host and manage a new site for Thunderbird and SeaMonkey add-ons. This new site,, will go live this week.

Starting on July 12th, all add-ons that support Thunderbird and SeaMonkey will be automatically ported to The update URLs of these add-ons will be redirected from AMO to the new site and all users will continue to receive automatic updates. Developer accounts will also be ported and developers will be able to log in and manage their listings on the new site.

Thunderbird or SeaMonkey add-ons that also support Firefox or Firefox for Android will remain listed on AMO.

If you come across any issues or need support during the migration, please let us know about it in this thread.


Thanks for the great work. I have logged on to the new domain and so far only found one problem: The statistics pages do not load - they show the spinner animation at the moment.

only some of the top level info (total number of downloads) are displayed.

One more thing - is the data migration of newer version still in progress?


lists 3.2.1 as newest version, but the actual current version number is 3.6

I have complete version histories on my support sites and want to make sure the version links with the updated domain will work:

(all headings currently link to AMO)

The statistics pages do not load - they show the spinner animation at the moment.

Yeah, this is a known issue. The software that parses the logs for statistics is not actually part of AMO, it’s a separate utility owned by the Mozilla internal data team. We’re still in the process of seeing if we can get access to this and get it set up. If not, we might have to figure out our own. TBD.

One more thing - is the data migration of newer version still in progress?

Yes, sorry if that wasn’t clear. The current ATN( database is a copy from ~December. AMO needed to turn off TB/SM submissions before we could copy the database again – otherwise any TB/SM changes between when we started the copy and ended it might not be included.

The copy will be done before we go officially live.

Other Known Issues:

  1. and android are still available for now. Eventually they will redirect back to, the redirects aren’t live to make it easier to look at the firefox sections as the process to delete Firefox-only add-ons runs.
  2. Currently emails are turned off, because the process to delete Firefox-only add-ons sends an email for each one deleted and that might overwhelm our mail provider. These are working and will be enabled later.

Note that is going down now for database and file copy and may be down for up to 24 hours.

Yes, sorry if that wasn’t clear. The current ATN database is a copy from ~December. AMO needed to turn off TB/SM submissions before we could copy the database again – otherwise any TB/SM changes between when we started the copy and ended it might not be included.

IF we submit new versions for The Thunderbird 60 release within the next week, should we use the new site or will this wreak havoc with the final imports?

Also, for “dual” Add-ons do they have to be submitted to both sites separately or are they “Linked” in some way?

After goes live(sometime tomorrow), you should upload new versions to it, yeah, because Thunderbird and Seamonkey-only addons will be deleted from the database entirely. There will be redirects activated on that will cause all previous versions of Thunderbird to check for updates going forward.

By “dual” add-ons I’m assuming you mean: Supports Firefox + Thunderbird/Seamonkey. Yes, those will need to be uploaded to both sites. However support for Legacy Firefox addons is going to be completely removed from at some point, likely in Q4, so that won’t be a concern. You’ll have to refer to the AMO team for specifics on how/when that will happen, though, because the Thunderbird team has no control over it.

P.S. The EFS file sync(this copies all the xpi files etc) is still in progress as of right now, and we don’t know how much longer it’s going to take, so the site will continue to be down until that’s done.

No redirects will happen from until this is done – hopefully by tomorrow.

I have, however, updated with a maintenance page.

Very good idea which I thank you for. I use a few essential security add-ons that are not supported by the WebExtensions API, extensions that were common to my firefox/thunderbird experience. These extensions are not going to be ported to the new ‘Quantum’ API and so ditching XUL will really leave me in the lurch. I have already migrated myself and my clients to Palemoon and I’m thoroughly happy to be in a XUL supported browsing environment and I strongly suggest you maintain it under Thunderbird for AS LONG AS POSSIBLE. I have been a user of Thunderbird from the beginning and it was due to its extensibility and ability to use the same XUL tools as my browser that I/we have been retained as loyal users. I was forced to abandon Firefox when it abandoned XUL support and I am fearful of the day when I will be forced to abandon Thunderbird. So, please make this seemingly temporary “stay of execution” for XUL a permanent one. I know this may be a tough decision for the TB team but as far as I am concerned the break from current FF needs to happen as soon as possible… Association with Firefox is an increasingly unhealthy connection and TB needs to break the connection and make its own way. There are alternatives.

To end positively, I love Thunderbird, love and support your recent decision and wish you well for the future.

Based on the current rate of progress, file sync is going to take another 24 hours. Redirecting on a Friday(the 13th… of all days, hah!) is a bad idea since any issue will mean forcing people to work on the weekend.

It is possible the site will go up tomorrow, but redirects from will not happen until Monday. It is also possible the site will not go up UNTIL Monday.

Further advisories will be posted both here and in the maintenance message on

The site has been available now for roughly 8 hours, and it seems to be running well. It’s safe to upload add-ons and do normal tasks on the site. There should not be any more database re-imports, barring anything unexpected. Note that we’re still organizing reviewers for the site, so reviews may be slow, but all AMO reviewers/editors have the same access to ATN as they do on AMO.

All Firefox-only add-ons have been deleted from the site, and and all similar URLs containing firefox redirect to AMO. Redirects for the Thunderbird and Seamonkey URLs have not been enabled on AMO yet, but they should be very soon(possibly July 17th). Also, emails(for review replies and such) should be enabled and functioning.

There may continue to be some minor issues this week as various non-essential bits are completed or new problems are discovered, but other than that we should be ready to go. File any issues at .

[sigh; score -1 for the new 2FA login scheme - I had to create a new Discourse account as my old one used my firefox email but setting up 2FA won’t let me access that. Grr.]

OK, so one of my extensions used to be for both Firefox and Thunderbird. As such, it’s not been migrated.

However, I had to rewrite it using WebExtensions for latest Firefox releases, so current versions don’t support Thunderbird.

I now need to post a patch release to set the compatible-with-Thunderbird 60 flag, so … what do I do?

Do I upload it as a “new” add-on to the new site? Will users automatically see it?

All links for themes go to a Not Found Page eg – – all links appear to go to 10900 which shows this

We’re sorry, but we can’t find what you’re looking for.
The page or file you requested wasn’t found on our site. It’s possible that you clicked a link that’s out of date, or typed in the address incorrectly.

@dbaker90 what theme did you push on to make it do this? Seems to be working now.

What extension is this? If it was marked compatible with Thunderbird, it should still be on the site. Only Firefox-only add-ons were removed.

Themes can only be installed via the add-ons manager in Thunderbird. This ‘not found’ link goes to the personas plus addon, which is not compatible with Thunderbird in any case. We should redirect this to some documentation, probably.

I see. So this happens when you click install. I’ve created a bug for this here:

My extension is URL Link (

The “latest” V3 is WebExtensions-only (thus so far Firefox only), the V2 branch is for Thunderbird support, and it’s this branch I need to update.

Unfortunately, AMO seems to have no concept of support branches, so I suspect the migration saw the latest was Firefox only without considering older-version support for Thunderbird.

I’m having trouble logging on to When I try to log on with the same account I use for, I am only offered to create a new profile (but not edit my existing data or profile). Where can I get help?

Hey @thenlich - could you Email me at I can walk through this with you and see if we can figure it out.

I just got a problem trying to update a ESR60 Add-on for Thunderbird. “cannot update a WebExtensions add-on with a legacy add-on.”

I have started to convert my ADd-on code so that Tb beta users can also use it so I have 2 separate xul files now. I would expect to be able to upload both, one for my current ESR crowd (legacy, install.rdf) and one for the “Bleeding edge” (manifest.json). But apparently, the later completely blocks me from supporting my existing “legacy” users? It should be possible to host both.

My existing ESR users would never be updated to the new version unless they install a Thunderbird beta, so the “downgrade” argument does not apply at all. I simply need to have 2 independent Add-on version trails because it is currently impossible to release a single Add-on xul that is compatible with both versions.