Add-on Compatibility for Firefox 27

Firefox 27 will be released on February 4th. This release cycle is slightly longer due to the holidays. Here’s the list of changes that went into this version that can affect add-on compatibility. There is more information available in Firefox 27 for Developers, so you should read that too.



  • Stop exporting JS symbols in Firefox. JSAPI is no longer available to extensions, which should only really be a problem for very specific binary add-ons. There are better ways to run JS in your extension anyway.


Please let me know in the comments if there’s anything missing or incorrect on these lists. If your add-on breaks on Firefox 27, I’d like to know.

The automatic compatibility validation and upgrade for add-ons on AMO will happen very soon, so keep an eye on your email if you have an add-on listed on our site with its compatibility set to Firefox 26.

8 comments on “Add-on Compatibility for Firefox 27”

  1. You Screwed Up Bigtime wrote on

    27 didn’t just disable all my add-ins, it removed them. Seriously, what is wrong with you people, I now have no extensions.

  2. Brandy wrote on

    Why is it the with this new update evey time i click on firefox icon it pops up add-on compatibility update everything i open firefox, this is very very anonoying since i have to cancel it just to get to my homepage….. there has to be a way to disable this very annoying window, until this is fixed or i can go back to 26.0 ill use IE !!!!! please fix since I really hate IE !!!

  3. UV wrote on

    This update is seriously annoying, you have taken a great product and turned it into somthing worthy of getting people to pull their hair out. Please fix this ridiculous addon compatibility check everytime firefox loads.

    A check is only required the 1st time FF27 runs and subsequently if someone installs a new addon .. not every time the browser starts.

  4. Luke wrote on

    The extension update check only runs once when it upgrades, and you can click “cancel” and it skips that step.

    The new update is nice, but there’s no mention here that changes in the devtools may require rewriting. I had to switch from dblclick to mouseup catching, since something was preventing bubbling of the dblclick event up to the window:

    but that’s a fairly rare use case though I’d imagine.

  5. Tricia wrote on

    I AM BEYOND DISGUSTED!!! For 2-3 months now, I have tried every suggestion available to GET RID OF THE COMPATIBILITY CHECK!!! and nothing works! This is such a waste of my time and beyond annoying! nothing ever changes and yet I must put up with this ridiculous ‘check’ every single time I start FF – I get the pop-up window that Firefox is checking add-on compatibility! Since I cannot seem to get this to stop, I will start using only GOOGLE CHROME! Thanks for ruining my day, again!

  6. buttduck wrote on

    Well, more people passing the buck, answer the questions people ! … You techies cant see the wood for the trees. You geeks need more daylight …. and me, i need less caffine ! …. Firefox – get rid of Compatibilty Check, it SUCKS … simple see ! = Everone will then be HAPPY and a better world for ALL — Nuff Said !

  7. Mike wrote on

    Compatibility check drove me mad, so am now using IE and Chrome.
    Why can’t you listen to the people who support your browser!!!

  8. Will Jones wrote on

    The Add-on compatibility check is a waste of space and the fact that Mozilla refuses to allow users to turn it off, suggests to me at least, that it is some sort of spyware designed to let Mozilla inflict us with even more bloody adverts. I’ve just downloaded the latest Internet Explorer and after writing this, will be removing Firefox and installing IE