Force Install Incompatible Firefox Extensions

Are you reluctant to upgrade Firefox because your favorite add-on is incompatible? If you tried to install it anyway, you might be faced with the following notice:

Extension Incompatible

Extension Incompatible Notice

Warning: Forcing to install extensions that are not updated to the current Firefox version may result in unexpected behavior. Continue at your own risk. Use Firefox Safe Mode to uninstall the add-on if anything goes wrong.

Method 1: Bypass Compatibility Check

Firefox checks if the add-on is compatible with the installed Firefox version during add-on installation. This check can be disabled through about:config.

Step 1: Type in about:config into the location bar. Click “I’m be careful, I promise!”. As it says, be careful here as this is like Firefox’s version of the Windows Registry.

Step 2: Type in ‘extensions.checkCompatibility’ (without quotes) into the filter box. If no results show, proceed to Step 3. If you find a boolean named ‘extensions.checkCompatibility’, toggle it so its ‘false’.

Step 3: Right click anywhere, and choose New, then Boolean.

Step 4: Type in ‘extensions.checkCompatibility’ and set the value as ‘false’.

New Boolean

Step 5: Restart Firefox and try installing your favorite extension again!

Step 6: If you are running Firefox 3.6, you must add an additional value: extensions.checkCompatibility.3.6 and set it to false.

Method 2: Nightly Tester Tools

The Nightly Tester Tools allows users to force install extensions regardless of their compatibility (assuming this add-on itself is compatible).

Method 3: Edit the Extension Compatbility

How does Firefox check if an extension is compatible? Inside the extension file lists the compatibility versions. Why don’t we edit that?

Step 1: Download the extension .xpi file by right clicking on the download button and clicking ‘Save Link As’ or by clicking the download button in another browser.

Step 2: Open the .xpi file with a Zip utility like 7-Zip (Windows). XPI files are zip  files with a different extension.

Step 3: Extract and edit the file named ‘install.rdf’. It can be opened with any text editor. Do not use a word processor.

Extension xpi

Edit the install.rdf file

Step 4: Search for a line with ‘<em:maxVersion>’.

Firefox Extension Version

Firefox Extension Version Compatability

Step 5: Edit the minVersion and maxVersion as needed. Wildcards are accepted. For example, for an add-on to install on all versions of Firefox 3.5, you would write ’3.5.*’ (without quotes). To force the QuickDrag to be compatible with Firefox 3.6 RC 1, I edited the file so that the targetApplication section looked like this (lines to edit are highlighted):


Step 6: Repackage the extension by compressing it into a zip file and renaming it into .xpi.

Step 7: Open the XPI file with Firefox by dragging it into the Add-ons window.

As I mentioned earlier, some add-ons might work perfectly, some might not work at all, some might have have strange behavior, and others may crash your browser. If something goes wrong, use Firefox Safe Mode to uninstall the extension. Force extensions at your own risk.

Brian is the co-founder of TechAirlines. He is a web developer and manages most of the site’s operations. He is currently a freshman at Stony Brook University, majoring in Computer Science.

  • Creastery

    Well…you can simply add 2 Boolean in about:config of Mozilla Firefox to get that done.

    Simply create extensions.checkCompatibility and extensions.checkUpdateSecurity and set both to false.

    extensions.checkCompatibility – If set to false, any add-on that is not suitable for your current Mozilla Firefox version can be installed, provided that extensions.checkUpdateSecurity is set to false.

    extensions.checkUpdateSecurity – This should be set to false if extensions.checkCompatibility is set to false as well. Any add-ons can be installed even if it does not meet the security requirements of Mozilla Firefox.

    Of course, use it at your own risk.
    Using incompatible add-ons can cause Mozilla Firefox to crash unusually.