I’m getting an error that says the “operating system loader has no signature” while trying to boot/start my computer. Because of this, the system either fails to start properly or shows a boot/security error screen.
I’ve already tried restarting the system, but the problem still exists. What causes this error, and how can I fix it safely without losing data?
The “Operating system loader has no signature” error usually appears when your system can’t verify the bootloader because of Secure Boot, corrupted boot files, or wrong boot settings.
Here are common fixes:
Restart and enter BIOS/UEFI settings
Enable Secure Boot (or reset it to default keys)
Make sure the correct boot mode is selected:
UEFI (recommended for modern Windows)
Check boot order and set your system drive first
Disable “Legacy/CSM boot” if enabled
Run Windows Startup Repair using a recovery USB
Rebuild boot files using Command Prompt:
`bootrec /fixmbr`
`bootrec /fixboot`
`bootrec /rebuildbcd`
Check if recent BIOS updates or OS changes caused the issue and rollback if needed
If nothing works:
Your bootloader may be corrupted or unsigned, and reinstalling the OS (Windows or Linux) might be required.
This error is common on systems using UEFI + Secure Boot when boot files get damaged or replaced incorrectly.