Every time a big Firefox release is upon us, we’re reminded of a longstanding and frustrating hassle on AMO: there’s only one latest version. Add-on versions and files are more complex than meets the eye, and in combination with our need for aggressive caching, AMO has only ever been able to return the very latest version of an add-on.
This becomes a problem around release time because developers may choose to upload an add-on that only works on the latest version, but it will strand users of the stable version. For example, if version 1.0 of my add-on supports up to Firefox 3.6.* and version 2.0 supports Firefox 4.0 and higher, as soon as I upload version 2.0, Firefox 3.6 users will stop getting updates and will see the add-on listed as incompatible on AMO except on the Old Versions page.
No more! As of a few weeks ago, the add-on update service will return the latest version compatible with your browser. If you’re using Firefox 3.6 and the latest version only supports Firefox 4.0, AMO will return the latest version that does support Firefox 3.6 on your platform.
Today we launched the second part of this fix, which will now support “backup versions”. If your add-on has a minVersion of 4.0 and you have previous versions that support a lower version, we’ll send both versions and only display the correct one. So, if you’re using Firefox 3.6 you’ll get the 3.6-compatible one as the latest, and if you’re using Firefox 4, you’ll get the Firefox 4 version as the latest. See FireFTP for an example of this in action.
We’re excited to finally have this support and hope that this will remove another barrier to compatibility updates for Firefox 4 and future versions.