Windows Logon UI won't load: black screen at login fix

You type your password, hit Enter, and instead of your desktop you get a black screen with a cursor. Or maybe the spinning circle keeps going forever. This happens most often after a bad Windows Update, a forced shutdown during profile loading, or when a third-party shell tweak (like StartIsBack or ExplorerPatcher) conflicts with the login process. I've seen it dozens of times on Windows 10 22H2 and Windows 11 23H2.

What's actually going on

The LogonUI process (logonui.exe) handles the login screen and user session initialization. When it hangs or crashes, the shell (explorer.exe) never starts. The system is technically logged in—you can sometimes launch Task Manager with Ctrl+Shift+Esc—but the graphical interface is stuck. The root cause is usually one of three things:

1. A corrupt user profile (default profile or your own)
2. A hung logonui.exe that didn't exit cleanly
3. A broken shell replacement in the registry

Fix it in 10 minutes

Skip the fancy recovery tools. Here's what works, in order.

Step 1: Kill the hung process

Press Ctrl+Shift+Esc to open Task Manager. If that doesn't work, try Ctrl+Alt+Del then select Task Manager. Look for Windows Logon Application or logonui.exe under Processes. Right-click it and select End task. If it doesn't show up, go to Details tab and find logonui.exe there. After you kill it, Windows usually re-launches it automatically. If you get a login screen again, try logging in. If the black screen returns, move to Step 2.

Step 2: Boot into Safe Mode

Force a restart three times—hold the power button during boot, let it fail, repeat. On the third boot you'll see the Recovery screen. Go to Troubleshoot > Advanced options > Startup Settings > Restart. Press 4 for Safe Mode. If Safe Mode loads your desktop, the problem is likely a third-party service or driver. But if you still get the black screen in Safe Mode, it's a corrupt profile.

Step 3: Rebuild the user profile

In Safe Mode, log in as a different admin account (use the built-in Administrator if you have one enabled). If you don't have a second admin account, enable the built-in one:

net user administrator /active:yes

Now open Registry Editor (regedit). Navigate to:

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

Look for a folder with a .bak extension—that's your original profile. Also find the one without .bak that ends with .pst or has a RefCount and State value. If you see two identical SIDs (one with .bak), delete the one without .bak, then rename the .bak one to remove the .bak extension. Reboot and try logging in. This forces Windows to rebuild the profile from the backup copy.

Step 4: Check the shell registry entry

If the profile fix didn't work, a third-party shell or a bad registry tweak might be blocking explorer.exe. Open Registry Editor and go to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

Look for the Shell value. The default should be explorer.exe. If it's anything else (like explorer.exe,StartIsBack64.dll or a path to another app), change it back to just explorer.exe. Also check the same key under HKEY_CURRENT_USER—some apps set per-user shell overrides there. Delete any non-standard shell values under HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon.

Still stuck? Try these

• System File Checker: Boot from a Windows install USB, open Command Prompt (Shift+F10), run sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows. Replace C: with your actual system drive.
• DISM: In the same Command Prompt, run DISM /Image:C:\ /Cleanup-Image /RestoreHealth.
• Check for pending updates: Sometimes a stuck update causes this. Boot into Safe Mode with Networking, run Windows Update manually, and install any pending updates.
• Last resort — system restore: If you have a restore point from before the issue started, roll back. Boot to Recovery, go to Troubleshoot > Advanced > System Restore.

If none of these work, you're looking at a corrupt system beyond quick repair. Back up your data from Safe Mode or a bootable Linux USB and do a clean install. It's rare, but sometimes the profile hive is too far gone to fix. I've had to do it maybe twice in 14 years. Don't waste a day on it—if the registry fix didn't take, reinstall.