Cross-browser testing requires using as wide range of browsers as possible. It’s most effective when you have all those browsers on one machine. We at CivicActions have written in the past about installing multiple IE browsers, but what about Firefox?

I recently downloaded Firefox 4 to see what the fuss was about, but right after installing, I realized I needed my old 3.6 version for client work. I didn’t want to switch back entirely, so I looked into running them both at once. Turns out, it’s very simple. You simply need to make sure the two applications have different names, and use separate Firefox profiles for each.

So if you want to check out Firefox 4, but not lose 3.6, here’s what you do (the process works in reverse too, if like me, you’d already downloaded 4 but want to have 3.6 too):

  1. Download Firefox 4, but instead of dragging the program icon into your Applications folder, drag it onto the desktop.
  2. Rename the program “Firefox4” or something similar, to distinguish it from your currently installed version. Now you can move it to the Applications folder.
  3. Do not start Firefox 4 yet. We need to create a new profile first. Open up Terminal (Applications -> Utilities -> Terminal) and enter the following commands:

    cd /Applications/Firefox4.app/Contents/MacOS/
    ./firefox-bin -ProfileManager


    Click “Create Profile” and follow the instructions. You only need to enter a new name, everything else can stay as a default.
  4. Select your new profile to start Firefox. If you don’t want to run this command every time you start, you can uncheck “Don’t ask at startup” so you can always choose when launching either version.


That’s it! When you decide to finally move on, simply drag the old version of Firefox into the trash and delete the profile.