Using multiple versions of Firefox simultaneously

Since Firefox 3.5 is out I’ve been looking for a way to run multiple versions of Firefox at the same time, just like MultipleIE.

I’ve been using portable versions of Firefox (via portableapps.com) to this end but was never quite happy with it, the main draw back being that you can’t run multiple versions simultaneously. You’d have to close one instance of Firefox (say, 3.0) to launch another (e.g. 2.0). That sucks.

So I’ve been looking around and found a much better approach which should work under Windows, Mac and Linux. You’ll have to change path and names, though.

Be smart and back up your existing profiles!

This is what I came up with:

Download Firefox

Installation:

I’m using Windows, so my program path is something like C:ProgrammeFF2 (respectively FF3). You’ll might be using another path, in which case you’ll have to change every path below.

Start Firefox:

Create a shortcut on your desktop and enter

C:ProgrammsFF2firefox.exe --no-remote -P ff2

The first part of that statement is the path to your Firefox version, the --no-remote enables running multiple instances of the application with different profiles and the -P launches the profile manager with the profile “ff2” (you’ll might want to rename that). “default” is your standard profile.

More about command line arguments for Firefox at Mozillazine.

Repeat that for every Firefox version the you want to use. Note that you’ll want to change the “ff2” corresponding to your Firefox version. Your “default” Firefox 3.5 installation is probably linked to your “default” profile.

Create Profiles:

Start your applications through your shortcuts. Your profile manager should pop up. You have to create a profile for every new Firefox version you’ve just installed. While you’re at it you might want to save your profile to another location than the default – e.g. to an encrypted partition or some folder that is regularly backed up.

Your profile has to have the same name as the one specified before (in the corresponding short cut), here “ff2”.

That’s it!

You’ll might want to move your shortcuts somewhere more suitable. Please also note that your new Firefox versions have none of your favoured add-ons installed – you should install them now.

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