How to Fix “Operating system loader failed signature verification” Error in Windows 11 Seeing the message “This operating system loader failed signature verification” during boot can be alarming. It usually means Secure Boot has blocked Windows from starting because it detected an issue with the bootloader’s integrity. In this video, we'll show you how to fix this error in Windows 11. Before we begin, be sure to subscribe to NinjaOne’s IT video hub and our YouTube channel for more tech content like this. Methods to Fix the “This operating system loader failed failed signature verification” Error in Windows 11 Method 1: Temporarily Disable Secure Boot This method is used for diagnostic purposes. To disable Secure Boot temporarily: Reboot the system and press F2, DEL, or ESC to enter the BIOS/UEFI Setup. Find Secure Boot under Boot, Security, or Authentication. Then, set Secure Boot to Disabled. Finally, save the changes and reboot your device. If the system boots normally after this change, the issue is likely related to the Secure Boot signature check. You can use the other methods we'll discuss to resolve this issue permanently. Method 2: Use Startup Repair from Installation Media Use this method when the bootloader is intact but misconfigured or partially corrupted. First, boot from a Windows 11 USB drive. Then, choose Repair your computer > Troubleshoot > Advanced Options > Startup Repair. Let windows attempt to automatically fix boot issues, then restart your PC to verify if the issue is solved. Method 3: Repair Boot Configuration with Command Prompt If the error persists, rebuild the BCD using Command Prompt. To do so, boot into the Windows recovery environment. Choose Troubleshoot > Advanced Options > Command Prompt, then run the following commands: If access is denied, assign a drive letter to the EFI partition and then run bcdboot C:\Windows /s S: /f UEFI Once done, close the Command Prompt and restart your device. Method 4: Check and Recreate the EFI Boot Partition The final method should only be done by advanced users to prevent system issues, and when all other methods have failed. To use this method, boot into the recovery Command Prompt. Run the command diskpartlist diskselect disk 0list partition to Launch DiskPart to inspect partitions. Identify the EFI partition and assign a drive letter to it with the command Next, recreate the boot files using the command Finally, reboot the system to apply the changes. For more information, check out our official blog post on How to Fix “Operating system loader failed signature verification” Error in Windows 11 linked in the description below.