Mozilla Firefox uses a Firefox account to synchronize your passwords, bookmarks and other navigation data between devices. If you leave behind Firefox, you can delete your account to delete all your personal data from Firefox servers.
Caution: This will eliminate the data of the Firefox browser stored online. However, all data stored in the Firefox browser on your computer will always exist, but will not be synchronized with your other devices.
Remove your account from Mozilla Firefox
If you're still logged in to your account from Firefox, click the menu button, then click your account name at the bottom of the Firefox menu.
Click "Manage Account" on the Sync Options page. Will take you to the account management page on the Firefox website.
Click the "Delete" button to the right of the Delete account at the bottom of the page.
Enter a password for your Firefox account and click the "Delete Account" button. Your account will be deleted. To create a new Firefox Sync account, you can.
Delete account from another browser Firefox
To delete your account without using Firefox Sync Firefox, go to the Firefox login page. Sign in with the email address and password you used for your Firefox account.
Scroll down and click the "Delete" button to the right of the Delete account.
Enter the Firefox account password again and click the "Delete Account" button. Your account will be deleted.