Add-on Compatibility for Firefox 55

Firefox 55 will be released on August 8th. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 55 for Developers, so you should also give it a look. Also, if you haven’t yet, please read our roadmap to Firefox 57.


Recently, we turned on a restriction on Nightly that only allows multiprocess add-ons to be enabled. You can use a preference to toggle it. Also, Firefox 55 is the first version to move directly from Nightly to Beta after the removal of the Aurora channel.

XPCOM and Modules

Let me know in the comments if there’s anything missing or incorrect on these lists. We’d like to know if your add-on breaks on Firefox 55.

The automatic compatibility validation and upgrade for add-ons on AMO will happen in a few weeks, so keep an eye on your email if you have an add-on listed on our site with its compatibility set to Firefox 54.

4 responses

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  1. vimmaholic2000 wrote on :

    So Vimperator will stop working? Fuck.


    1. that-random-guy wrote on :

      Not just that, but soon CTR will stop functioning as well.

      A disappointment and a poor judgement being passed only to introduce a lack-luster “substitute” that only compliments so much of what we want.

      It’s ironic how even in their own polls, it’s concluded that people were fine with how things were.

      A small percentage of those who actually participated in the biased poll were those asking for what results after WebExtensions.

      I guarantee you, nobody wanted this. Nobody.


  2. AndrewL wrote on :

    Beginning with FF53, new XUL based products won’t be signed in the AMO store, so they must be a WebExtension. However WebExtension is only supported on FF48+, so for those users on FF43-47 (where signing is enforced) what are we supposed to serve them since we can’t get a XUL extension signed?


    1. Jorge Villalobos wrote on :

      Updates to existing extensions are still allowed. Only new extensions need to be WebExtensions.


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