How to Enable Old Firefox Extensions in Firefox 4

Every Firefox Upgrade, many Firefox Add-ons stop working. The reason can be anything right from compatibility to other issues. Sometimes there is no issue but only because the Add-on was set to Work with  say , 3.X  , Firefox says the add-on is not compatible. Though Firefox 4 can automatically update Add-ons automatically but you still need to wait.

Steps to make Firefox Add-on Work in Firefox 4 :

  • Launch a new tab in Firefox
  • Type about:config
  • Confirm that you want to edit advance settings.
  • Right click anywhere and select New > Boolean
  • Type in the preference name as “extensions.checkCompatibility.4.0″
  • Next window set it as false.
  • Done this it will add another configuration item with details you just added.

Enable Old Addons in Firefox 4

Enabling the disabled add-ons :

The first thing you should do now is check for existing add-ons which where disabled. Go to Add-ons Manager and select extension tab. You will notice that some apps are enabled but will work only when you restart Firefox but some are not and you will have to manually enable this. This is because of some security or stability issues.

Like you can see below, the extension of HP works fine but Skype has security issues.

Compatibility Tests on Fly in FF 4

How to enable compatibility check again :

Any time you want to turn the compatibility check on, you dont have to come here again.  Go to Add-ons Manager ( File > Addons ) and you will see a warning enabled which says “Add-on Compatibility checking is disabled…”. Right next to this you will have Enable Link.

Enable Add-ons compatibility check

However once you enable this, you will not  get an option to enable it from here. And  the configuration item which you just added above changes from boolean to string. This means you will have to delete the old one and add another one as boolean. This happens when you have about:config open.

Extensions Check Compatibility changes to String

In case you see the same. Close the about:config and reopen it. You will notice that its gone. Now repeat the steps again.


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