How to Fix a LogonUI.exe Error at Windows Sign-In

A LogonUI.exe error appears while Windows is loading the sign-in interface. Common triggers include damaged Windows files, a faulty display or biometric driver, third-party sign-in software, a recent update, or unstable memory. Do not download LogonUI.exe or a DLL from a file-sharing site; replacing protected system files with an unverified copy can create a security problem or prevent Windows from starting.

Try a clean restart

Disconnect nonessential USB devices, docks, and external displays, then restart once. If the sign-in screen appears, log in and immediately back up important files before continuing.

Open Windows Recovery Environment

If Windows repeatedly fails before sign-in, it normally opens Automatic Repair. Select Advanced options > Troubleshoot > Advanced options. If it does not, boot from official Windows installation media and choose Repair your computer—not Install.

Run Startup Repair first. It is designed to correct startup configuration and file problems without removing personal files.

Use Safe Mode to undo a recent change

From Advanced options, select Startup Settings > Restart, then press 4 for Safe Mode. TipsMake's Safe Mode guide covers other entry methods.

In Safe Mode:

• Uninstall sign-in customization, facial-recognition, fingerprint, theme, or security software added just before the error.
• Open Device Manager and roll back a recently changed display or biometric driver when the option is available.
• Remove only the specific Windows update that immediately preceded the failure, then restart and test.

Get replacement drivers from Windows Update or the PC manufacturer's support site. Avoid generic driver-download tools.

Repair protected Windows files

If Safe Mode opens, launch Terminal (Admin) or Command Prompt (Admin) and run:

DISM.exe /Online /Cleanup-image /Restorehealth
sfc /scannow

Wait for each command to finish, then restart. Our guide to repairing Windows files with SFC explains how to interpret its results.

If Windows cannot enter Safe Mode, do not reuse the /Online command blindly from recovery media: drive letters and offline-image syntax differ in Windows Recovery Environment. Use Startup Repair, System Restore, or a technician familiar with offline DISM servicing.

Try System Restore or uninstall the triggering update

In Windows Recovery Environment, select System Restore and choose a restore point from before the error. System Restore affects system files, drivers, and installed applications, but it is not a substitute for a current backup.

If the problem began directly after a Windows update, use Uninstall Updates and remove the latest quality update first. Avoid removing multiple updates without testing between changes.

Check memory if errors vary

Faulty or unstable RAM can cause changing application errors. If Windows can start, search for Windows Memory Diagnostic and schedule a restart test. Repeated hardware errors, random crashes, or corrupted files warrant a deeper memory test and professional hardware inspection.

Last recovery options

If the problem remains, back up files from a trusted recovery environment if possible. Then consider Reset this PC or a clean reinstall using official Windows media. Review Windows boot-recovery options before choosing a method that removes applications or data.

Windows 7 and Windows 8 are no longer supported. The recovery concepts are similar, but an internet-connected PC should be upgraded or replaced rather than restored to an unsupported configuration.