Are you dying to try out firefox 4 but not ready to give up firefox 3? You can run them both safely on your apple os x system. Here is how to do it. Updated for latest versions of firefox.
This technique will work for running any prior versions of firefox. Previously, this tutorial covered running Firefox 2 and 3 concurrently. This has now been updated to cover firefox 3 and 4.
When you install firefox 4 normally in os x, the process will overwrite your firefox 3 installation. Especially during the beta phase, you may not want to completely upgrade just yet. Here is how you can have firefox 4 and firefox 3 on your system.
1. Download firefox 4
2. Click on it to start the installation process
3. Instead of dragging the firefox icon to your application folder, drag it to the desktop top.
4. Select the firefox icon and press enter. Rename the firefox application to something more appropriate. I used firefox_beta, for example.
5. Drag the renamed application to the application folder.
6. Run firefox 4.
If you want to uninstall firefox 3 and revert back to firefox 2, just drag the firefox 3 icon to the trash.
Next, you will want to protect your firefox 3 profile. Create a new profile before running firefox 4.
1. Open the Terminal
2. type cd /Applications/Firefox.app/Contents/MacOS
3. type to run the ProfileManager: ./firefox-bin -ProfileManager
4. Create a new Profile and select it.
Here is an example of them running side-by-side:
Now all your firefox installations will run the new profile. If you decide you no longer want to run firefox 4, then repeat the process to revert your profile back to your default before you delete firefox 3. If you want to continue to run firefox 4 with your old profile (and bookmarks, etc), then switch the profile over to your old default profile.