Updated: June 20, 2008
With Firefox 3 finally released, it is time to upgrade and enjoy the new features and the performance increase it offers. But, the truth is we have learnt to trust our current profile in Firefox 2 and naturally you’d be leery of upgrading to Firefox 3. For good reasons. There are still some extensions that haven’t been updated for Firefox 3.
But, with all the hype that’s going on with Firefox 3 (I am guilty of that too
) and if you are curious to play with it without messing your current Firefox 2 setup, here is how you do it.
If you have read my previous article on Backing up your Firefox profile, you are already familiar and comfortable with using Profiles. Although recommended to read my previous post, it is not essential to follow the few easy steps in this How to.
- Create a New Profile: You can create a profile exclusively for Firefox 3 in your Firefox 2 Profile Manager. Name it something like DeleteMe so you know you are just testing it.
From your command prompt,
c:\Program Files\Mozilla Firefox\firefox.exe -ProfileManager ( for Windows) - Download Firefox 3: Download the latest Firefox 3.
- Install Firefox 3: You have choose a different installation folder than the default one as choosing the default will overwrite your current Firefox 2! You could also choose to get the Portable Firefox 3.
- Start Firefox 3: Start Firefox 3 with the new DeleteMe profile you created. The key here is the ‘-no-remote’ parameter as it makes Firefox start a second Firefox.exe process with the new profile

From your command prompt,
d:\firefox3\firefox\firefox.exe -P DeleteMe -no-remote
( for Windows – I unzipped the Firefox 3 nightly build to D:\firefox3 directory)

You could also create a Desktop Shortcut and change the property of the shortcut to look like in the Picture below so you don’t have to type it all in every time.
You could run your Firefox 2 simultaneously with Firefox 3 because they are both using different Profiles.
Now that I have Firefox 2 & Firefox 3 simultaneously, you can safely try it out and see which extensions work and which don’t before actually making the switch.
(Thanks Chu Yeow for sharing this trick.)
New: If you are on Mac OSX, you could have an donationware application MultiFirefox maintain these profiles for you and switch between them without getting your hands dirty. [via TUAW]
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