This feature requires Firefox version 67 and above.

What are profiles?

Firefox saves information such as bookmarks, passwords and user preferences in a set of files called a profile. This profile is stored in a location separate from the Firefox applicationprogram files. More details on profiles can be found here.

What profile changes were made in Firefox 67?

Some users have multiple installations of Firefox, each in separate applicationprogram folders. These separate Firefox installations previously shared a single profile by default. Starting with Firefox version 67, Firefox uses a dedicated profile for each installation of Firefox (including Nightly, Beta, Developer Edition, and ESR installations). This makes Firefox more stable when switching between installations on the same computer and also allows you to run different Firefox installations at the same time.

Tip: To see what Firefox version you're on, see To see what Firefox version you're on, see Find what version of Firefox you are using

You will not lose any personal data or customizations. Any previous profile data is saved and associated with the first Firefox installation that was opened after this change.

What are my options?

If you do nothing, your profile data will be different on each installation of Firefox. If you would like the information you save to Firefox to be the same on all installations, you can use a Firefox Account to keep them in sync. Sync is the easiest way to make your profiles consistent on all of your installations of Firefox. You also get additional benefits like sending tabs and secure password storage. Get started with Sync here.

Can I change which Firefox install uses my previously shared profile?

Yes. You can use the Profile Manager for each installation, to set a new default profile. Directions are available in the Profile Manager article. See also the Recover user data missing after Firefox update article.

I am a Sync user, will my saved data still remain synced?

Yes. Once you sign in to your Firefox Account on Firefox, any data saved to Sync from other installation of Firefox should appear.

What happens to my profile if I downgrade to a previous version of Firefox?

You’ll have to create a new profile to avoid corruption issues.

Starting with Firefox version 67, each Firefox installation requires a separate profile. Any previous profile data is saved and associated with the first Firefox installation opened after the change.

If you try to launch a Firefox installation with a profile that was last used in a more recent version, you'll see a warning that using an older version of Firefox can corrupt profile data such as bookmarks and browsing history:

Click the Create New Profile button to start Firefox with a new profile.

When you downgrade Firefox and use a new profile, any profile that was used in the higher version is still available in the Profile Manager, for use in a more recent version of Firefox.

Note: Downgrade protection can be overridden by launching Firefox through the command line with the --allow-downgrade parameter.

I already use separate profiles for my different Firefox installations

If you have already manually created separate profiles for different installations, you will not notice the change (this has been the recommended procedure on Nightly for a while).