See: *https://support.mozilla.org/en-US/kb/Uninstalling+Firefox You may want to use the Profile Manager to remove the Firefox profile folder where Firefox stores your personal data before uninstalling Firefox if you do not intend to reuse Firefox. *https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Firefox uses two locations in a hidden location for the Firefox profile folder. Location used for the main profile that keeps your personal data in "AppData\Roaming" (Root Directory on about:profiles). *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\ Location used for the disk cache and other temporary files in "AppData\Local" (Local Directory on about:profiles). *C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>\