So you installed a new version of Firefox or installed an update and now your favorite extension is no longer working. It has been disabled by Firefox. Do you want to re-enable your favorite extension or want to install an incompatible extension in Firefox?
Don't worry! You have come to the right place. This tutorial will help you in making your favorite extensions compatible with Mozilla Firefox and will also help you in installing incompatible extensions.
Many times a few already installed extensions are automatically disabled after updating Firefox version or you can't install a new extension because its not compatible with Firefox version. It happens because the developer didn't update the extension or the developer failed to code the extension compatibility version properly.
Anyway there are a few possible methods, which can be used to make any extension working in Firefox even if it was disabled because of the compatibility issues:
- Using Nightly Tester Tools extension
- Using Add-on Compatibility Reporter extension
- Using Firefox built-in about:config tool
A. Using Nightly Tester Tools Extension:
"Nightly Tester Tools" is a great extension for Mozilla Firefox which can help you in installing an incompatible extension or enabling an already disabled extension.

You can download it from following link:
It also provides many other useful features like:
- Customize Firefox titlebar text
- Copy build tag to clipboard
- Copy list of installed extensions to clipboard
- Open profile folder
- Take screenshot
B. Using Add-on Compatibility Reporter Extension:
Add-on Compatibility Reporter is an official Mozilla Firefox extension developed by Mozilla itself which automatically enables incompatible extensions and let you report them to Mozilla.
This extension allows you to test whether your favorite extensions still work with the version of Firefox that you're using. If you notice that one of your add-ons doesn't seem to be working the same way it did in previous versions of the application, just open the Add-ons Manager and click Compatibility next to that add-on to send a report to Mozilla.

You can download and install it using following link:
Download Add-on Compatibility Reporter
Thanks to our readers "Archy" and "carbonize" for mentioning it...
C. Using Firefox built-in about:config Tool:
1. Type about:config in Firefox addressbar and press Enter. It'll confirm, click on I'll be careful, I promise! button.

2. Now right-click and select "New -> Boolean". Give it name:
extensions.checkCompatibility.3.6 (For Firefox 3.6)
extensions.checkCompatibility.4.0 (For Firefox 4.0)
extensions.checkCompatibility.5.0 (For Firefox 5.0)
extensions.checkCompatibility.6.0 (For Firefox 6.0)
extensions.checkCompatibility.7.0 (For Firefox 7.0)
extensions.checkCompatibility.8.0 (For Firefox 8.0)
extensions.checkCompatibility.9.0 (For Firefox 9.0)
extensions.checkCompatibility.10.0 (For Firefox 10.0)
extensions.checkCompatibility.11.0b (For Firefox 11.0 Beta)
extensions.checkCompatibility.12.0a (For Firefox 12.0 Alpha)
extensions.checkCompatibility.13.0a (For Firefox 13.0 Alpha)
And set its value to false.
3. Again right-click and select "New -> Boolean". Give it name extensions.checkUpdateSecurity and set its value to false.
4. That's it. You have done. Restart your browser and now all disabled extensions will be enabled and you'll be able to install new incompatible extensions as well.
NOTE: You can also change value of extensions.lastAppVersion to the version no which is compatible with your favorite extension. After installing the extension, you can revert back the value. It'll not affect the installed extension.
BONUS TIP: There is another method to hack .rdf file of the extension and change the maxversion value to make the extension compatible. But its a complicated method and is not required or recommended when we have the above mentioned easy methods.
This article was posted by VG in following section: Mozilla Firefox, Troubleshooting.
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Ben Pesso
Hey, any idea how to deauthorize extensions with NTT? I think I broke FF3.5 when I forced all extensions on it, but there's no "undo" button for "un-forcing" the extensions. :$
Oscar
when I installed the nightly tester..it cannot install after restart...my ff is 3.5.2, but it never happen on 3.5.1
Aqua
It worked! Thank you so much for this tutorial! :)
Ray Maruschak
extensions.checkCompatibility. -- what type of entry? Boolean? Integer? String?
If I put = 3.6 does that mean FF will check to see if addon is compatible with 3.6 and will block addon if it is not compatible with 3.6? So to make addon work with 3.6 I should put = 3.7?
I tried extensions.checkCompatibility.3.6 as string, but it didn't work to allow addons to work with 3.6.
You can also change value of extensions.lastAppVersion to the version no which is compatible with your favorite extension.
???
-- what type of entry? Boolean? Integer? String?
Addon don't work in 3.6. So what I set extensions.lastAppVersion to? 3.5? I don't understand how this is supposed to work to allow me to use addons that report "Not compatible with FF 3.6".
VG
^^ Please check the "IMPORTANT" section given in Method B. Firefox 3.6 uses a different Boolean value.
BOB
THIS IS AWESOME! I LOVE IT
THANKS A LOT
Archy
If it hasn't already been mentioned, Mozilla has its own ""Add-on Compatibility Reporter" for use with Minefield builds. That allows you to not only use unconfirmed add-ons, but to report their state to Mozilla. I think it's worth a mention.
Cheers
ugugx
hey, i was wondring if you can share your them up there with us as your green theme is fantastic but it's time to change it by now, thnx
MJPollard
The MR Tech Toolkit extension also allows overriding compatibility checking for extensions, plus it offers a whole host of other "bare metal" configuration options. And, it's available for both Firefox and Thunderbird.
carbonize
I'm with Archy. The easiest way is to install the Add-on Compatibility Reporter which automatically disables the compatibility check and lets you report that an add on is working. Would love to know why thi s has yet to be added to the main article.