What sfc /scannow does, how to read its results, where the CBS.log is and when to run DISM first.
System File Checker (sfc.exe) is a Windows tool that scans protected system files and replaces damaged or missing ones with correct copies from the component store. The common command is sfc /scannow, run from an elevated command prompt; results are logged in C:\Windows\Logs\CBS\CBS.log.
'Windows Resource Protection did not find any integrity violations' means the protected files are fine.
'found corrupt files and successfully repaired them' means repairs were made; restart the PC.
'found corrupt files but was unable to fix some of them' usually means the component store is damaged: run DISM /Online /Cleanup-Image /RestoreHealth and then sfc /scannow again.
sfc /verifyonly scans without repairing. sfc /scanfile=<path> checks one file. /offbootdir and /offwindir let SFC repair an offline Windows, for example from the recovery environment.
sfc /scannowLast updated: 2026-10-08
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