How to uninstall Firefox Developer Edition on Windows
Back up bookmarks, passwords and extensions before removing Firefox Developer Edition. In the browser, open Help › More Troubleshooting Information and use Profile Folder › Open Folder to identify the profile you actually use; close Firefox before copying it to a backup. Mozilla explains profile backup. This guide covers the machine-wide winget installation, not a portable copy.
Remove Developer Edition
Quit every Firefox window and check Task Manager for remaining firefox.exe processes. Use Settings › Apps › Installed apps › Firefox Developer Edition › Uninstall, or run:
winget uninstall --id Mozilla.Firefox.DeveloperEdition --exact
Mozilla's uninstall instructions distinguish removing the program from removing profile data. Check that you are removing Developer Edition rather than the regular Firefox installation.
Preserve the correct profile
| Observed location | What to do |
|---|---|
%ProgramFiles%\Firefox Developer Edition |
Let the uninstaller remove the program |
%APPDATA%\Mozilla\Firefox |
Holds Firefox profiles and profile selection data; back up the active profile and keep others |
%LOCALAPPDATA%\Mozilla\Firefox |
Holds local profile data; inspect the matching profile rather than deleting the whole parent |
Developer Edition and other Firefox installations can have data under the same Firefox parents. Do not remove those parents just because Developer Edition is gone. The test also left a profile-count file in a shared Mozilla directory under ProgramData; it is not a reason to delete the shared directory. Uninstalling does not delete a Mozilla account or remove data from other synced devices.
Check the result
Get-Process firefox -ErrorAction SilentlyContinue
winget list --id Mozilla.Firefox.DeveloperEdition --exact
Test-Path "$env:ProgramFiles\Firefox Developer Edition"
Test-Path "$env:APPDATA\Mozilla\Firefox"
Test-Path "$env:LOCALAPPDATA\Mozilla\Firefox"
No process output means no firefox process is running; an existing process may be regular Firefox, so check its path before stopping it. No winget match means the Developer Edition installation record is gone. True means that path remains and False means it is absent; retained profile folders are expected. Errors leave the check unresolved, and a surviving program folder needs inspection.
What Mole lists
The program folder, matching shortcuts, usage records, startup entry and registrations still pointing at this installation are selected by default. The Local and Roaming Firefox data folders are personal data, listed but not selected and never selected by a bulk action; deleting either requires an individual choice after checking every profile inside. The shared ProgramData profile-count file is not listed, and firewall rules are reported rather than removed.
What this test covered
Tested on October 3, 2026 with Firefox Developer Edition 156.0, AArch64 English-US, through winget machine-wide installation on an ARM64 VM. The test removal set included both personal profile folders, so the result does not establish UI bulk-selection behavior. All listed removal items were removed or already absent. A shared ProgramData profile-count file remained. Real bookmarks, passwords, account sync, coexistence with regular Firefox and a separate vendor-only uninstall were not verified.