Here’s a handy tool for Firefox users and an explanation of its use from nirmaltv. Read on:

Profile manager is an inbuilt tool in Firefox to create multiple profiles in Firefox. This is useful if you want to run a profile without any add-ons installed. We have covered Profile Manager for Firefox previously on this blog. The profile manager was not directly accessible in Firefox through any of the menus, but now Firefox has an external app called Profile Manager for Firefox.

via Profile Manager for Firefox.