User profile service failed the logon

Seeing “The User Profile Service failed the logon” or being logged on with a temporary profile almost always comes down to one of two causes: a corrupted registry entry for that specific user’s profile, or a corrupted default user profile template affecting every new logon.

Existing User Can’t Log On (Temporary Profile)

Windows duplicates the profile’s registry key with a .bak suffix when it detects a conflict, then creates a temporary profile instead of loading the real one. To fix it:

1. Open Registry Editor and navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList

2. Find the SID key ending in .bak and the matching SID key without it.
3. Check the ProfileImagePath value on each — the one pointing to the correct UNC/local profile path is the genuine original.
4. Rename (or delete) the duplicate that isn’t the original, then rename the .bak key by removing the .bak suffix so it matches the original SID again.
5. Log off and back on.

New Users Can’t Log On, But Existing Users Can

This points to a corrupted Default user profile — the template every new profile is built from. Replace the corrupted Default folder (under C:\Users\Default) with a clean copy taken from a healthy machine on the same Windows build. Always back up the registry keys and folders you’re about to change before editing, since incorrect edits to ProfileList can affect other user profiles on the machine.

Still Correct on Windows 11 (2026), Now With an Official Citation

The manual fix above — renaming the .bak SID key under ProfileList, or replacing a corrupted Default profile folder — remains the correct approach on current Windows 11 (23H2 through 25H2); the underlying profile-loading mechanism hasn’t changed. It’s also not just a community workaround: Microsoft maintains an official “Fix a corrupted user profile” support article that documents this same registry/ProfileList process as the sanctioned method, rather than pointing to a separate automated repair tool, so it’s worth treating the manual steps here as Microsoft’s own current guidance rather than a legacy trick.

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