Multifox 3.1.0 No Restart
An extension that allows Firefox to connect to websites using different user names. Simultaneously.
*** Multifox 3 – Now with PER-TAB profiles *** https://getmultifox.com/
*** Multifox 2 users: try the "Window Mode" (see screenshot below) ***
This add-on is not compatible with your version of Firefox because of the following: