Run Firefox 5+ and Firefox 3.6 side by side on Windows

(Edit: Corrected instructions so that HTTP links in other apps will still open in Firefox.)

There’s an intranet application that I need to use that does not work in Firefox 4, Firefox 5, Chrome, Opera, or Safari. It also runs painfully slowly in Microsoft Internet Explorer 8. Since it does support Firefox 3.6, I thought I’d try running two different versions of Firefox side by side.

1. Install Firefox if you don’t have it. At the time of writing, the latest stable version is Firefox 5.
2. Download Firefox 3.6.
3. Start the installation and choose the Custom installation type.
4. Install it to a non-standard location such as “C:Program FilesMozilla Firefox 3.6”
5. I recommend telling it to not create any shortcuts, as it will otherwise overwrite the Firefox 5 shortcuts.
6. Open up the folder where you keep your Firefox shortcuts. Make a copy of one of them.
7. Right-click -> Properties and add -ProfileManager to the target path (not the “Start in” field)
• "C:Program FilesMozilla Firefoxfirefox.exe" -ProfileManager
8. Make sure Firefox is closed and launch that shortcut. It will open up the Firefox Profile Manager.
9. Create a new profile. Name it something like: Firefox36
10. Close the Profile Manager.
11. Configure the main shortcut as follows:
• Mozilla Firefox
• "C:Program FilesMozilla Firefoxfirefox.exe" -P default
• "C:Program FilesMozilla Firefox"
• Note: An earlier version of this post added the -no-remote parameter to the command line above. This prevented HTML links in other applications (e.g. Outlook, Lotus Notes) from using this browser. You only need to set it on one of the two shortcuts, and I’ve modified the instructions accordingly with the assumption that this shortcut is to your primary browser.
12. Configure the other shortcut as follows:
• Mozilla Firefox 3.6
• "C:Program FilesMozilla Firefox 3.6firefox.exe" -P Firefox36 -no-remote
• "C:Program FilesMozilla Firefox 3.6"
13. Voila!

Links

• Firefox command line arguments