How To Disable Strict Add-On Compatibility In Firefox

Martin Brinkmann
Nov 17, 2011
Updated • Nov 20, 2012
Firefox, Firefox add-ons

One of the biggest issues that Firefox users have with the rapid release cycle introduced earlier this year is the fact that updates often disabled their add-ons in the browser due to incompatibilities. Most of the time though those incompatibilities can be attributed to the maximum compatible version number assigned to an add-on, and not to technical incompatibilities. Many Firefox users made use of Nightly Tester Tools or the Add-on Compatibility Reporter to force add-on compatibility.

This behavior is finally going to change with the release of Firefox 10. For now, the new feature has been implemented into recent Nightly versions of Firefox 11. The technology is disabled by default and needs to be activated before it can be tested.

Mozilla plans to integrate the override ability into Firefox 10 Aurora soon and then in the beta and stable channels when they hit version 10 as well.

To disable strict add-on compatibility in Firefox, users need to enter about:config into the browser and filter for the key extensions.strictCompatibility.

extensions strict compatibility

The default state is true which means that strict add-on compatibility is enabled. This means that Firefox will disable add-ons that are not compatible with the version of the browser.

A double-click on the entry and the selection of False turns strict compatibility off. What this means is that Firefox will assume that add-ons are also compatible with the updated version of the browser.

There are a few exceptions to the rule though that need to be listed here. While it is possible to force add-on compatibility this way, it does not ensure that add-ons are indeed compatible with the more recent version of the browser. If add-ons are technically incompatible with the new version of Firefox, then forcing them to be compatible won't change that fact; The add-ons will remain incompatible. But there are other requirements. Add-ons with binary components will be ignored by the new directive, as will add-ons with a minimal compatible version that is higher than the version of the web browser.

Add-on developers lastly can force their add-ons to be strictly compatible. (via)

Update: I noticed that the latest Aurora version is already listing the extensions.strictCompatibility parameter.


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  1. Harvey said on November 17, 2011 at 6:32 pm

    Say, I checked my config file and that particular key is not listed!
    Can I enter it manually?
    Using FF 7.01

    1. Martin Brinkmann said on November 17, 2011 at 6:45 pm

      Harvey, you will have to wait until you have Firefox 10 on your computer.

  2. Straspey said on November 17, 2011 at 4:49 pm

    I have one question about this:

    Would this work for backwards compatibility as well ?

    I’m running Firefox 3.6.24 and I am unable to download and try out many of the
    newer extensions and themes, as they are designed for the newer versions of FF.

    Could I use this work-around to force these extensions to load into my current
    version ?

    1. Martin Brinkmann said on November 17, 2011 at 5:16 pm

      Straspey, no it won’t work. Two reasons for that. First, automatic compatibility is blocked if the browser version is lower than the minimum required version of the add-on. Second, the new feature will only be available in Firefox 10 and newer.

      1. Straspey said on November 17, 2011 at 5:59 pm

        Martin –

        Thanks very much for your helpful reply.

        I suspected that would be the case, and I’m glad I asked you before trying it out and possibly doing some damage.

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