From MozillaZine Knowledge Base



This preference allows for an override of the version number used when checking extension compatibility. As of Firefox 2.0b1, this preference has been replaced by extensions.checkCompatibility.

Possible values and their effects

A numeric version number (ex: 1.4.1). By default it is not defined, and extension compatibility checks uses the true application version number.


  • This preference does not exist by default.
  • Installing an extension marked as incompatible with your application may cause your application to misfunction.

Previous effects

This preference used to be the source of the version number rather than an override.

First checked in

2004-07-12 by Ben Goodger.

Has an effect in

  • Firefox (all versions from 1.0 to 2.0b1)
  • Thunderbird (all versions since 1.0 to 2.0b1)

Related bugs