How To Run Multiple Firefox Versions Simultaneously (FF3.x & FF4)

Acquire FF installers here:

• For the latest Firefox browser version visit Mozilla Homepage.
• For old versions visit Old Apps.

1. Install Firefox 4 on C:\Program Files\Mozilla Firefox 4 (upon installation select "custom" to specify the directory when to install FF)

2. Install Firefox 3.x on C:\Program Files\Mozilla Firefox 3 (upon installation select "custom" to specify the directory when to install FF)

3. Create a desktop shortcut for both FF

4. Right-Click on Firefox 4 shortcut then click Properties

5. In the Shortcut Tab add this line to Target field -p PROFILE -no-remote

Example  : "C:\Program Files\Mozilla Firefox 4\firefox.exe" -p PROFILE -no-remote

6. Click OK

7. Double-Click on the Firefox 4 shortcut , then FF profile manager will appear

8. Create a profile for both FF3 and FF4  (see above).
Note: You'll probably only see one profile named "default." All you have to do is create a new profile for Firefox 3, but you may want to rename your existing profile to keep things tidy. I choose "Firefox3" and "Firefox4," ideally use a name with no space in it. Then click Exit

9. Again Right-Click on Firefox 4 shortcut then click Properties.

10. In the Shortcut Tab replace again Target field -p PROFILE -no-remote with -p Firefox4 -no-remote.

Example: "C:\Program Files\Mozilla Firefox 4\firefox.exe" -p Firefox4 -no-remote

11. Do Step 10 to other Firefox 3 shortcut but with -p Firefox3 -no-remote

Example: "C:\Program Files\Mozilla Firefox 3\firefox.exe" -p Firefox3 -no-remote

12. There you go, FF3.x and FF4 browsers in your machine.