Add-on Compatibility for Firefox 11

Firefox 11 was pushed to the Aurora channel weeks ago, and Firefox 12 will follow suit very soon. So, it’s time for the long overdue overview of bugs that can affect add-on compatibility in Firefox 11. I’m sorry this update is being posted so late, but things have been pretty crazy lately. More on that in the Firefox 10 section.

A few notes regarding Firefox 10

If everything goes according to plan, Firefox 10 will be pushed to the public in less than a week. There are a couple of points that are worth mentioning:

  • Starting with Firefox 10, add-ons will default to compatible. All add-on versions that have compatibility up to Firefox 4 or higher will automatically work in Firefox 10 and all future releases. This excludes add-ons that are not extensions (themes, dictionaries, language packs) and add-ons with binary components. We will also keep an override list that we will fill with all add-on versions that are known to break due to compatibility problems. This is what has kept me busy for the past weeks. We need your help to keep the override list up to date.
  • Rename omni.jar to omni.ja. If your add-on references omni.jar directly, it will break now that it has been renamed. We recommend that you find more flexible ways to reference these files, since most should be accessible through chrome URLs.

For more information about Firefox 10 compatibility, please read the full compatibility update.

Firefox 11

Other important changes are noted in Firefox 11 for developers.

New stuff in 11!

Please let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 10 or 11, I’d like to know.

Because of the Default to Compatible feature, we are no longer doing compatibility bumps like we did before. We will still run the validation but only send you a message if your add-on is identified as incompatible. There will be no more automatic version upgrades, given that there’s no point anymore.

24 comments on “Add-on Compatibility for Firefox 11”

  1. Kohei Yoshino wrote on

    I just posted the Japanese translation:

    1. Jorge Villalobos wrote on


  2. Mark Banner wrote on

    I’ve just done a test – the Canadian Dictionary is not marked as incompatible in TB 10, despite the fact that it says max version 10.0a1 on the AMO website.

    1. Jorge Villalobos wrote on

      I could be wrong about dictionaries. They should work fine across versions, unlike language packs or themes, that always require significant work to update.

  3. Mingyi Liu wrote on

    Default to compatible is great! One of my Jetpack addons was mysteriously marked as incompatible with FF9 despite that I marked it as compatible up to 10 and it was tested & working in 9 and 10beta. This did not happen to other Jetpack or non-Jetpack addons of mine and dumbfounded me. Users were emailing me about it too and I had to post a special note on addon page. Now hopefully I don’t need to worry about this issue any more!

  4. suryaden wrote on

    translating into bahasa Indonesia on my blog

  5. MarkD wrote on

    Instead of releasing a new firefox every few hours, why don’t you just focus on making the current one fast, efficient, reliable and compatible? Not everyone wants to update their web browser every week.

    Just a thought.

    1. Sam Streubel wrote on

      I agree, this is nuts for the average user. With the update to FF10 I lost the Google toolbar with all the addons and haven’t the faintest idea how or where to re-install them.

  6. Mats Svensson wrote on

    So you STILL cant sidegrade from 3.5 if you have addons you need that 4.0+ broke?


    1. Jorge Villalobos wrote on

      Add-ons that weren’t upgraded to 4 are very unlikely to work on current versions of Firefox.

      Which add-ons do you need that are not compatible with 4?

  7. Victor Kimuar wrote on


    I’m wondering if there is a nofollow addon for firefox 10. Or where is the page where I find only firefox 10 addons?


  8. cal wrote on

    why i cant use avg safe search plugin in firefox 11?

    1. Jorge Villalobos wrote on

      You should contact AVG if you still have this problem.

  9. Almander Yaza wrote on


    I’ve a question. I’ve not updated my Firefox since 3.6.22, I know I need to. But I really enjoy the addons and things that work on this version. Is there a way to find out if all the addons and things I use will work in Firefox 11 or 12? I want to switch but I don’t wanna lose what I have. I am open to other innovations but not at the cost of losing what I have. Anyone have an idea?

    1. Jorge Villalobos wrote on

      We plan to post a few add-on-related guides in the following weeks, which will include recommendations for add-ons that are no longer being updated, and other ways to facilitate making the switch. In general, you can check on AMO if you want to see the compatibility level for your add-ons, but you can also post the list here and I’ll let you know.

  10. Charles wrote on

    Food for thought … upgrades should make life easier, not harder. I upgraded to firefox 11 and lost free download manager add-on. Switched back to 7.0.1 and have no regrets. Perhaps Firefox 13 or 14 should contain all the ‘bug fixes’. Referring users to third party vendors like AVG is akin to suggesting that we should try another browser.

    Like I said … food for thought.

  11. Shimul Kibria wrote on

    Can anyone help me out getting the “Acrobat Create PDF” addon for Firefox 11?
    Adobe Acrobat Create PDF 1.1 works only with “Firefox 3.6.x”.

    Any suggestions?

    1. Jorge Villalobos wrote on

      If this is an add-on that generates PDFs out of web pages, I don’t know of any alternatives. I see a few on AMO but I haven’t tested them.

      There are also many free PDF printers you can install on Windows. No add-on involved.

      1. Shimul Kibria wrote on

        Thanks Jorge…

        I’ve chosen the add-on Save as PDF 1.5 created by Pdfcrowd Team. Its working fine even with Firefox 12.0.

        Thanks for your help, do take care! 🙂

  12. Geno wrote on

    Firefox 11 shows the ‘tinyurl’ add-on as installed and compatible yet I don’t see it appearing in the add on toolbar at the bottom of the browser. I also don’t see anywhere to enable the add on or a button to access it. Am I missing something here?

    1. Jorge Villalobos wrote on

      Can you point me to the add-on you’re referring to? It’s possible the button was removed from the toolbar. One thing you can try is to open the toolbar customization dialog and see if the button is there and just hasn’t been added to a toolbar.

  13. ED LEWIS wrote on

    I keep getting MOzilla message that we have obsolete firefox which is 3.6.28 and that I must download version 12, but it does not download.

    I am using XP

    I turned off Norton antivirus and it did not download 12

    Got any ideas why it does not download?

    Thanks, ed lewis

    1. Jorge Villalobos wrote on

      Have you tried downloading it directly from

  14. Stan wrote on

    Firefox automatically updated me to version 12. Now I don’t have the Norton addon that keep all my autologin passwords etc. How do I get that back? Not very happy right now.