Mac OS X only: Run multiple versions of Firefox side by side and quickly switch between profiles with donationware application MultiFirefox. If the Firefox 3 hubbub has convinced you to upgrade but not all of your must-have extensions have caught up yet, MultiFirefox lets you get used to Firefox 3 in one window while sticking to your tried-and-true extensions in Firefox 2. From another perspective, switching between user profiles on Macs is a pain, and this app provides a simpler point-of-access to the Profile Manager. MultiFirefox is donationware, Mac OS X only. If all you want to do is run different profiles and you don't want another app to do it, here's how to manage multiple Firefox profiles.