Add-on Compatibility for Firefox 43

Firefox 43 will be released on December 15th. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 43 for Developers, so you should also give it a look.




  • This is the first version of Firefox that will enforce signing. Unsigned add-ons won’t install and will be disabled by default. There’s a preference that turns signing enforcement off (xpinstall.signatures.required in about:config), but the current plan is to drop the preference in Firefox 44.

Please let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 43, I’d like to know.

The automatic compatibility validation and upgrade for add-ons on AMO will happen in the coming weeks, so keep an eye on your email if you have an add-on listed on our site with its compatibility set to Firefox 42.

20 comments on “Add-on Compatibility for Firefox 43”

  1. Kohei Yoshino wrote on

    Posted Japanese translation:

    1. Jorge Villalobos wrote on


  2. Simon wrote on

    What’s the current timeline on enabling e10s in a release?

    1. Jorge Villalobos wrote on

      Here’s the current schedule. I think the current estimate is to release e10s with Firefox 45.

  3. Ken Saunders wrote on

    I haven’t been able to find any information on the status or location or even news on an undranded build except for a (vague) bug listing. Will you please point me to some decent sources pertaining to this?

    1. Jorge Villalobos wrote on

      There haven’t been any status updates, except that it is expected to ship on time. I’m afraid the bug is the best source of information (for all of us).

  4. Chaofan Wu wrote on

    Hi, now I have one legacy XUL-ovelay extension and I know this will be obsolete in the future. Also I see there are two alternatives, Addon-SDK extension and WebExtension API. I have 2 questions:
    1. I want to use WebExtension API because this is the preferred way in the future but I’m afraid that this is still in early stage and cannot provide enough functionality as Google Chrome. So when will Mozilla provide an stable WebExtension API for development?
    2. What’s the future of Addon-SDK,? I see low-level API will be affected by multi-process Firefox, does this mean low-level API cannot work well in the future even though we have CPOW as a special choice now?

    1. Jorge Villalobos wrote on

      1. The API is planned to be stable and be released officially early next year.
      2. Not all low-level APIs are affected by e10s, but some will break and the SDK isn’t getting much development support at the moment. CPOWs are a hack to keep some add-ons working after the move to e10s, but you shouldn’t rely on them.

      1. Chaofan Wu wrote on

        Thanks a lot.
        And one more question, for extension development what kind of role will Addon-SDK play in the future? coz we will have WebExtension API as the first choice. Will Addon-SDK get enough support as WebExtension API in the future even after XUL/XPCOM is deprecated?

        1. Jorge Villalobos wrote on

          No, the SDK will also be phased out, and we will try to migrate extensions from the SDK to WebExtensions with as little effort from the developer as possible.

  5. Lopo Lencastre de Almeida wrote on

    A few of my add-ons stopped working.

    Dojo Firebug Extension 1.1.5b2 [DISABLED]
    Download Statusbar [DISABLED]
    EventBug 0.1b10 [DISABLED]
    FireSass for Firebug 0.0.12 [DISABLED]
    Mailvelope 0.8.3 [DISABLED]
    NetExport 0.9b7 [DISABLED]
    Social Fixer 11.2 [DISABLED] 0.4 [DISABLED]
    Ubuntu Firefox Modifications 2.7 [DISABLED]

    Some are very annoying being disabled as I do need them daily 😛

    1. jason wrote on

      NetExport has been replaced with a signed “Har Export Trigger”

  6. A concerned user wrote on

    I get enforcing signed addons by default, but removing the preference for it in the future is a step which is obviously taking control away from the user. It makes sense for me to use this preference and I would have to ditch firefox if I couldn’t anymore. Please consider keeping your security feature optional for those who don’t want/need it.

    1. Kevin M wrote on

      Removing the preference not a good idea. I had all my key add ons disabled with the update to 43 and had to figure out how to flip the bit to ignore this. Take away my ability to choose and you just drive me further into the hands of Goog and Apple.

  7. Melissa Maddox wrote on

    I do love my Yahoo Toolbar add-on, but I have updated the Firefox 43, and the Yahoo toolbar (DISABLED) I wanted my Yahoo toolbar back working again!. Because I had to check my Yahoo mail and weather even news. I had a Amazon button on toolbar. Please bring back the toolbar to add-on in Firefox 43.

  8. Enforcing signed addons terrible idea wrote on

    Enforcing signed addons in future versions of FireFox is a terrible idea, it removes user flexibility and freedom to do as they please with their browser.

    I hate to say this, but I will also have to ditch FireFox if they do this and as much as I hate it, go back to Chrome.

  9. Rex Bryant wrote on

    FoxLingo is disabled in Firefox 43. I use(d) it several times a day for definitions and translations.

    There are forum reports (rumors?) that the latest version of “FoxLingo” now contains some
    “Superfish” ad-ware, though I haven’t experienced that and have not found a definitive credible source saying so. Is this why FF43 disabled FoxLingo? Or do their developers need to update it for signing in Firefox?

    For now I’ll turn off the signing requirement in about:config and see what transpires in the next month. I’ve an xclnt FW and AV but this is not a permanent solution.

    Thank you for a great browser,
    Regards, Rex

    1. Jorge Villalobos wrote on

      It looks like the add-on was abandoned a while ago, and there haven’t been any submissions for signing, at least not with the original add-on ID. It’s up to the developers to submit a version for signing if they wish to continue supporting it.

  10. Laurent Viaud wrote on

    “the current plan is to drop the preference in Firefox 44”

    Firefox 43 just disabled a bunch of very useful add-ons , including featured ones, like Tab Mix Plus.
    I don’t know why they’re still unsigned but breaking add-ons so frequently was bad enough.
    If I start losing even working add-ons (even temporarily) with every update I’ll just have to stop updates until they’re verified (and probably start looking for another browser).

    Please stop killing FF’s flexibility.

    1. Jorge Villalobos wrote on

      Tab Mix Plus is signed. There’s a bug we’re investigating where some add-ons appear as unsigned. Reinstalling the add-on generally fixes this problem.