I need to change the user agent on several computers that are using Firefox. Using the useragent setting in about:config worked for several of the computers that are using an older browser. However, several PCs are using Firefox 7. Here, I am using the general.useragent.override setting to change the user agent, but this does not remain in place after I close and reopen the browser. I also tried downloading the Firefox extension that allows you to set the useragent, but I can not find a way to set the new useragent by default; it all requires manual interaction from the user upon launch of the browser.

Is there a way to set the default useragent? (Preferably one that does not involve the registry).


  • 2
    If you are willing to mess around with about:config, how is the registry different?
    – user1686
    Oct 24 '11 at 14:16
  • 2
    Also, general.useragent.override still works. It could be that Firefox does not store preferences to prefs.js on exit? Check if other settings are stored.
    – user1686
    Oct 24 '11 at 14:20
  • @grawity: the difference between about:config and the registry is that 1) the about:config is much easier to grasp, IMHO, and that 2) I can only break Firefox through the about:config, but I could break much more through the registry.
    – user95156
    Oct 24 '11 at 17:28

I can't find anything in the change logs that the general.useragent.override preference was made temporary with Firefox 7. Bug 582421 is still open which begs to differ if there's something else messing with your prefs. It should only change (or rather reset) when upgrading Firefox.

You can always try with the addon UAControl. However, it can only set the user agent automatically on a per site basis, not globally.

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