I haven’t had the need to do this yet but thanks to @StephenCronin asking this question.
With Firefox 4 out yesterday, there are many extension developers who haven’t updated their add-ons yet. Or you may want to test your website on Firefox 3 while using Firefox 4 simultaneously.
Whatever the reason maybe, here is how you can run Firefox 4 and Firefox 3 at the same time.
Only requirement to do this you have to use 2 different profiles. You don’t want to mess with a stable profile anyways.
- Launch Firefox 4 from the Run command with the flags ‘-profilemanager –no-remote’ (without the quotes)
Windows: “C:\Program Files\Mozilal Firefox4\firefox.exe” -profilemanager -no-remote
Mac/Linux: //firefox4/firefox -profilemanager -no-remote
- Select your Firefox 4 profile
- Launch Firefox 3 from the Run command with the flags ‘-profilemanager –no-remote’ (without the quotes)
Windows: “C:\Program Files\Mozilal Firefox3\firefox.exe” -profilemanager -no-remote
Mac/Linux: /firefox3/firefox -profilemanager -no-remote
- Create a Firefox 3 profile if you don’t have one already and select it
This assumes you want to keep your current profile on Firefox 4. Just reverse it if you want it the other way.
This should let you run Firefox 4 and Firefox 3 simultaneously. You can also create shortcuts with these flags in place to launch them easily.