Multiple Firefox

Use Multiple Firefox Instances

This tip happens to be my favorite Firefox tip/tool. With it, you can run many instances of Firefox with different Profiles and different Firefox versions at the same time.
The benefits:
Run test and beta versions of Firefox without affecting your default Firefox configuration,
Use different Profiles for different users without having to shut down Firefox,
Test new extensions and themes in a new Profile before incorporating them into your default Firefox Profile, and other uses which you’ll discover as you use this tip.

1) Open Notepad and paste in the following:
@echo off
set MOZ_NO_REMOTE=1
start "" "C:\Program Files\Mozilla Firefox\firefox.exe" -p
set MOZ_NO_REMOTE=0


2) Save the File
Save the file with any name that you wish, and in any location, but you’ll be saving it as a .bat


3) Run the File
Now assuming that you have more than one Profile, when you double click
on the .bat file, the Profile Manager should open up allowing you to
choose a Profile to run in addition to your currently opened Firefox Profile.