A reinstall can fix Firefox when the installation is damaged, extensions are broken, or normal troubleshooting has not helped. For a true clean start, remove both the app and the Firefox profile data; for a gentler reinstall, leave the profile folder alone so bookmarks and saved information return.
Does this affect you?
Use this for Firefox on Windows 10, Windows 11, and macOS. The steps cover removing the browser itself and, optionally, deleting saved Firefox profile data.
Windows
Uninstalling from Windows Settings removes the program. Deleting the profile folder is optional.
- Close Firefox completely.
- Open the Start menu and choose Settings.
- Go to Apps > Installed apps. On Windows 10, use Apps > Apps & features.
- Find Mozilla Firefox, open the three-dot menu beside it, and choose Uninstall. Confirm the prompt.
- For a completely fresh profile, open File Explorer, type %APPDATA%MozillaFirefox in the address bar, and delete the Firefox folder. Skip this if you want bookmarks, saved passwords, history, and other profile data to remain.
- Go to mozilla.org/firefox and download the current installer.
- Run the downloaded installer and follow the prompts. Firefox opens when installation finishes.
Mac
On macOS, Firefox is removed like most regular apps.
- Quit Firefox completely by pressing Cmd+Q or right-clicking its Dock icon and choosing Quit.
- Open Finder and go to Applications.
- Drag Firefox to the Trash.
- Empty the Trash if you want to finish removing the app now.
- For a completely fresh profile, open Finder, press Cmd+Shift+G, enter ~/Library/Application Support/Firefox, and delete that folder. Skip this if you want Firefox data to come back after reinstalling.
- Download Firefox from mozilla.org/firefox.
- Open the Mac installer and drag Firefox into the Applications folder.
More control
Try Refresh Firefox first
Firefox has a built-in reset that often fixes the same problems with less disruption. Open the Firefox menu, go to Help > More troubleshooting information, and click Refresh Firefox. This resets settings and disables extensions and themes while keeping bookmarks, history, and saved passwords.
Know what data you are deleting
Uninstalling only the app usually leaves bookmarks, passwords, browsing history, and other profile data in place. Reinstalling Firefox picks that profile back up. Delete the profile folder only when you intentionally want that data removed too.
If a clean reinstall does not help
When Firefox still fails with a fresh profile, the cause may be outside the browser: antivirus filtering, a damaged Windows user profile, network filtering, DNS problems, or system-level proxy settings are common next places to check.
Sources
- Mozilla Support – Uninstall Firefox from your computer (2025)
- Mozilla Support – Refresh Firefox – reset add-ons and settings (2025)
- Mozilla – Download Firefox (2025)