02 April, 2011

Running Multiple Versions of Firefox on one PC

I decided that I wanted to update to Firefox 4 and yet also not yet have to upgrade my RoboForm (see prior posting) password/identity manager. Thus, I needed a means by which to run multiple versions of Firefox on the same PC.

I accomplished this by creating a new Firefox profile (called Dan_v3.6x), and then re-installing Firefox 3.6, in a separate folder, creating a shortcut, to the 3.6 executable, and adding an argument, after the shortcut's target location, to use the 3.6 profile when running the 3.6 executable.

I can now run both Firefox 4 and Firefox 3.6 on the same PC. The catch is that only one version can be running simultaneously, but it works great. [Note that if one tries to launch the other version, while one version is still running, the system will simply launch another window of the same version.]

So now, when I absolutely need my RoboForm information, it's there, but when I want the Firefox 4 experience, I can have that too.


  • Create a new Firefox profile
  • Run the Firefox Profiler Manager via the command prompt (or via creating a shortcut) as follows:
"C:\Program Files\Mozilla Firefox\firefox.exe" -Profilemanager
  • Install Firefox 3.6 into a custom folder via the 'Custom' installation option. I suggest the following:
C:\Program Files\Mozilla Firefox _3.6x
  • Create a shortcut to Firefox 3.6. exactly as follows, including quotes:
"C:\Program Files\Mozilla Firefox _3.6x\firefox.exe" -P "Dan_v3.6x"
The key to the above steps to work is that one needs to create a new profile, in Firefox 4, prior to installing the older version.

Downloading Older Firefox Versions:

To download Firefox 3.6 or other older Firefox versions, go here:

http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/ .

Jump to


for the Win32 version if you're a Windows 32-bit user.

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