
Firefox store a user's preferences and data such as installed add-ons, saved passwords, history, bookmarks and others in a unique profile. The first time you start Firefox, it automatically creates a default profile and stores all settings associated with the profile within a special profile folder on your computer.
Most users are unaware that they can create additional profiles in Firefox. Profiles are useful when there are multiple users on the same computer which all share the same user account. For example, the PC in your living room. Profiles can also be helpful in certain situations such as testing of new add-ons – use a “test” profile to test new add-ons, and if they work correctly, install them under your “default” profile. Similarly, you can keep separate profiles installed with different sets of extensions.
To create a new profile or manage existing profiles in Firefox, press Ctrl+R to open the Run dialog box and type “firefox.exe –p” as shown below.