System File Checker is a built-in Windows repair tool that scans protected system files and replaces damaged or missing ones with known-good copies. It is a sensible early repair step when Windows acts strangely and the cause is not obvious.
This guide applies to Windows 10 and Windows 11. The sfc command is included with Windows.
Does This Affect You?
Run sfc /scannow when Windows features stop working, apps crash unexpectedly, system errors appear, or troubleshooting points toward corrupted system files. It does not reinstall Windows or remove your personal files.
Run sfc /scannow
The scan commonly takes 10 to 20 minutes. Let it finish before closing the window.
- Click Start, type cmd, right-click Command Prompt, and choose Run as administrator.
- Run
sfc /scannow. - Wait until the scan reaches 100 percent. Do not restart or close Command Prompt while it is running.
- Read the final Windows Resource Protection message. It may say no integrity violations were found, corrupt files were found and repaired, or corrupt files were found but some could not be repaired.
- Restart the PC after the scan, especially if repairs were made.
Run DISM First if SFC Cannot Repair Everything
SFC uses the Windows component store as its repair source. DISM can repair that underlying Windows image so SFC has good files to use.
- Open Command Prompt as administrator again.
- Run
DISM /Online /Cleanup-Image /RestoreHealth. - Keep the PC connected to the internet. DISM may use Windows Update to download replacement files.
- Wait for DISM to complete successfully. It can take 15 to 30 minutes or longer on some PCs.
- Run
sfc /scannowagain, then restart.
Extra SFC and DISM Notes
Export the SFC Repair Details
To create a desktop log of SFC entries, open Command Prompt as administrator and run findstr /c:"[SR]" %windir%LogsCBSCBS.log >"%userprofile%Desktopsfcdetails.txt". The file can help identify what SFC repaired or could not repair.
Use an ISO as a DISM Source
If DISM cannot download repair files, mount a Windows installation ISO and point DISM at it with a source path such as DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:X:sourcesinstall.wim:1 /LimitAccess, replacing X: with the mounted ISO drive letter.
Recurring Corruption May Be Storage Related
If SFC repairs files repeatedly and the same problems return, check drive health. In PowerShell as administrator, Get-PhysicalDisk | Select-Object DeviceId, HealthStatus should report Healthy for each drive. Back up important files immediately if a drive reports trouble.
When Repairs Still Fail
If SFC and DISM cannot stabilize Windows, a reset or repair installation may be needed because the entire system image may be too damaged for individual file repairs.
Sources
- Microsoft Support: Use System File Checker to repair missing or corrupted system files
- Microsoft Learn: Repair a Windows image
- Microsoft Support: Fix Windows Update errors