Iceweasel and User Agents

So you just installed Iceweasel, but you are worried that some web site will not work because you are no longer running "Firefox"? While it's true that the the word "Firefox" does not appear anywhere in the user agent string in Iceweasel (though this may change in the future), most proper web sites don't care about the user agent, and the web site will Just Work(TM). Here is a typical user agent sent by Iceweasel:

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1) Gecko/20061024 Iceweasel/2.0 (Debian-2.0+dfsg-1)

And here is the user agent your browser is sending:

Mozilla/5.0 (compatible; archive.org_bot +

However, for that occasional web site that will only work under IE or "Firefox", there is a solution. There is an extension that lets you change your user agent on-the-fly. Moreover, this site has provided a definition file that lets you browse as if you were on Firefox 2 for Windows XP.


  1. Download this definition file to be imported later.
  2. Download and install the User Agent Switcher extension.
  3. Restart Iceweasel after installing.
  4. Go to Tools -> User Agent Switcher -> Options -> Options....
  5. Click the User Agents section, then click Import....
  6. Import the XML file you downloaded above.
  7. Click OK.

If you want to enter the information manually, here it is:


Now, when you need to, you can simply go to Tools -> User Agent Switcher -> Firefox 2 (Windows XP), and the web site will be none the wiser. You can test before/after by going here, which will show you what your browser is returning via Javascript and the User-Agent HTTP header.

The Ubiquitous FAQ

Should I use the Firefox 2 user agent profile all the time?

No! If the web were perfect, user agents would be useless because sites would be coded to standards, and the browsers would be fixed/tweaked to conform to those standards. Do your small part by using your Iceweasel browser, and only switch the the Firefox 2 user agent profile when needed.

If I'm running Linux, why are you recommending masquerading as a Windows XP machine?

Officially, because you should only be using the alternate profile when absolutely needed, and showing Win32/Windows XP will make it as easy as possible to view a broken site. Unofficially, when I wrote this guide, all of my Linux machines had already been switched to Iceweasel, and the only Firefox 2 installation handy was on a Windows XP machine.

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