How to fix error error-undefined-character in Windows 11

Solution Steps

1. 1 Press Windows key + R, type 'sysdm.cpl', and press Enter. In System Properties, go to 'System Protection' and create a restore point. Name it 'Before Undefined Char Fix'. This is a safety net.
2. 2 Press Windows key + X and select 'Windows Terminal (Admin)' or 'Command Prompt (Admin)'. Click Yes. This gives you the necessary permissions.
3. 3 Run 'sfc /scannow' and press Enter. This scans for corrupted system files that might be causing the error. It may take 15-20 minutes.
4. 4 After SFC, run 'DISM /Online /Cleanup-Image /RestoreHealth' and press Enter. This repairs the system image. It can take up to 30 minutes.
5. 5 Restart your computer. After reboot, try to reproduce the error. If it occurs when opening a specific file, try opening it with a different text editor like Notepad++ or Visual Studio Code, which handle various encodings better. You can also change the file's encoding: open the file in Notepad, click File → Save As, and in the 'Encoding' dropdown, select 'UTF-8' or 'ANSI' as appropriate.
6. 6 If the error occurs in a specific application, check for updates or reinstall the application. Also, ensure your system language settings are correct. Press Windows key + I to open Settings, go to 'Time & Language' → 'Language & region', and ensure the correct language is set.