• Windows
  • Browsers

Firefox splits its data across two folders and keeps old profiles forever

The profile and the cache live under different roots on Windows. How to tell which profile is live and what is safe in each.

5 min read

Firefox on Windows puts the profile in Roaming and the cache in Local, which catches people out: clearing the cache in settings empties one of them and leaves the other alone.

The two folders

Get-ChildItem "$env:APPDATA\Mozilla\Firefox\Profiles","$env:LOCALAPPDATA\Mozilla\Firefox\Profiles" -Directory -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue | Measure-Object Length -Sum).Sum
    [PSCustomObject]@{ MB = [math]::Round($s/1MB); Path = $_.FullName }
  } | Sort-Object MB -Descending
RootHoldsSafe to clear
AppData\Roaming\MozillaThe profile: bookmarks, history, extensions, logins, site storageNo, this is your browser
AppData\Local\MozillaThe disk cacheYes, entirely

Telling which profile is live

Type about:profiles into the address bar. Every profile is listed with its exact folder path and the one in use says so. Do not guess from folder names: they are random strings with a label after them and the labels repeat, which is why nobody dares delete any of them.

What is large inside a profile

  • storage\default. Site storage, IndexedDB and service workers. Not cleared by clearing the cache, and usually the largest part.
  • places.sqlite. History and bookmarks. Small, and not something to remove.
  • extensions. Installed add ons.
  • sessionstore-backups. Recovery copies of open tabs. Safe to clear, and you lose tab recovery.

Clearing site storage properly

Settings, Privacy and Security, Cookies and Site Data, Manage Data lists it per site with sizes. Removing the three largest sites usually gets most of the space without signing you out of everything.

Profiles from previous installs

A reinstall, a refresh or a channel change creates a new profile and leaves the old one. Anything in the Profiles folder that about:profiles does not list is an orphan. That is the same trap as Firefox on a Mac, where the folders differ and the behaviour does not.

Common questions

Where is the Firefox profile folder on Windows?

In %APPDATA%\Mozilla\Firefox\Profiles for the profile itself, with a separate cache under %LOCALAPPDATA%\Mozilla\Firefox\Profiles. Typing about:profiles shows the exact paths.

Why does Firefox have several profile folders?

Reinstalling, refreshing or switching channels creates a new one and leaves the previous profile behind. Nothing removes them, so a machine that has had Firefox for years has several.

Does clearing the Firefox cache free much space?

Usually not. The cache is bounded, while site storage under storage\default in the profile is not, and clearing the cache does not touch it. Site data is cleared per site in Settings.

Is it safe to delete an old Firefox profile?

Yes, provided about:profiles does not list it as in use. Check first, because an old profile can still hold bookmarks and logins that were never copied across.

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