What is a Profile and Why Do I Need One? A profile in Firefox is a collection of bookmarks, browser settings, extensions, passwords, and history These items are stored in a special profile folder on your hard drive. Firefox uses a default profile to store all of your personal settings. Profiles are extremely handy for those who test nightly Firefox builds, as well as those who develop extensions. If you use a separate profile for testing or development purposes, and something goes horribly wrong (e.g., all your data gets lost), you still have your "default" profile to fall back on (the data there is still safe). If you use different configurations or versions of Firefox for testing, profiles can be preconfigured and reused.

Make sure all instances of Firefox are closed. Select Start » Run from the Windows Start menu.

Type the following command and click OK: firefox -ProfileManager

In the resulting Profile Manager window, click the Create Profile button.

Click the Next button in the profile creation wizard.

Choose a dedicated folder for your future Firefox profile.

In the second step of the wizard, provide a name for the new profile and click the Finish button.

Back in the Profile Manager, select your new profile from the list on the right and click the Start Firefox button.