Blog

Install Firefox 3.6 add-ons in Firefox 4 beta, disable compatibility check

Posted on June 30, 2010

Firefox 4 beta is available. I installed the 64bit version on Linux today, it’s notably faster than previous versions and includes several other improvements such as tabs on top. Now, I don’t want to go back to 3.6.

As usual the only thing holding me back from upgrading is add-on compatibility. Luckily it’s possible to disable the compatibility check so Firefox 4 will let you install add-ons built for older versions, I found that many add-ons work just fine in Firefox 4.

Disable compatibility check

If you’re willing to take your chances, navigate to about:config in your browser, promise not to break anything and right to window click to add a new boolean. In the preference name field, add extensions.checkCompatibility.4.0b and set the value to false. Firefox will now let you install any add-on.

If anything breaks, try disabling add-ons or delete them completely. You can always go back to 3.6 if nothing works, and wait for a new stable release.

I’ve tested it with AdBlock Plus, Firebug, Flashblock and Wappalyzer.

Scroll to top