The sfc (System File Checker) command scans all protected Windows system files and automatically replaces corrupt or missing ones from a compressed backup cache.
Random crashes, Blue Screen of Death errors, and unexpected system behavior are often caused by corrupt system files — sfc is the first tool to run when these occur.
Quick Answer
Open Command Prompt as administrator and run sfc /scannow. The scan takes 5–15 minutes and automatically repairs any corrupt system files it finds.
How to Use the sfc Command on Windows
Method 1: Run sfc via Command Prompt or PowerShell
This is the standard method for running a system file scan — it works on a normally booted system and covers the majority of corrupt file scenarios.
Open Command Prompt as administrator from the Start menu, then run the command below. The scan verifies all protected system files and repairs any it can access.
sfc /scannow
To view detailed scan logs, paste the path below into the Windows Run box (Win+R) to open the CBS.log file where sfc records every action it takes.
%WinDir%\Logs\CBS\CBS.log
To extract only the SFC-related entries from the log file and save them to a separate text file, run the findstr command below in an elevated Command Prompt.
findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log > C:\sfclogs.txt
Method 2: Run sfc via Windows Recovery Environment (WinRE)
Use WinRE when the system won’t boot or when sfc fails with “cannot perform the requested operation” in normal mode — it scans files offline without Windows interfering.
Hold Shift and click Restart from the Start menu to enter WinRE. If you can’t boot at all, interrupt the boot process three times and Windows will open WinRE automatically.
Navigate to Troubleshoot ? Advanced Options ? Command Prompt, then run sfc /scannow — the scan runs against the offline Windows installation.
Method 3: Run sfc in Safe Mode
Safe Mode loads only basic drivers, which allows sfc to access and replace files that are locked by running services in a normal boot environment.
Enter WinRE, go to Troubleshoot ? Advanced Options ? Startup Settings, click Restart, and press 6 to boot into Safe Mode with Command Prompt.
Once Safe Mode with Command Prompt loads, run sfc /scannow — the reduced driver environment allows the tool to repair files that are normally in active use.
sfc Command Flags Reference
| Flag | What It Does |
|---|---|
/scannow |
Scans all protected files and repairs corrupt ones |
/verifyonly |
Scans for integrity violations — no repair |
/scanfile=path |
Scans and repairs a specific file by full path |
/verifyfile=path |
Verifies a specific file — no repair attempted |
/offbootdir=dir |
Specifies boot directory for offline scans (WinRE) |
/offwindir=dir |
Specifies Windows directory for offline scans (WinRE) |
How to Fix “Windows Resource Protection Could Not Perform the Requested Operation”
This error means sfc could not access a file it needed to repair — typically because the file is locked by a running process or the Windows image itself is corrupted.
Run the offline scan from WinRE using the command below — replace e:\ with your actual boot drive letter and c:\Windows with your Windows installation directory.
sfc /scannow /offbootdir=e:\ /offwindir=c:\Windows
When sfc Fails: Use the DISM Command
If sfc cannot repair the corrupt files, run DISM first — it repairs the Windows component store that sfc uses as its repair source, then re-run sfc afterward.
DISM uses Windows Update to download a clean copy of any damaged component. Run it from an elevated Command Prompt — an internet connection is required for this command.
DISM.exe /Online /Cleanup-Image /RestoreHealth
After DISM completes, run sfc /scannow again — with a repaired component store, sfc can now find and apply replacement files it previously could not access.
When to Run sfc /scannow
Run sfc when Windows shows random crashes, application errors, or missing DLL messages — corrupt system files are a common cause of all three of these symptoms.
Run sfc after a failed Windows Update or an interrupted system upgrade — the update process can leave files in a partially replaced state that sfc can detect and repair.
Run sfc in Safe Mode or WinRE if normal mode scans keep reporting errors — some system files cannot be replaced while they are actively loaded into memory by Windows.
Related Guides
These Windows diagnostic tools work alongside sfc to fix drive errors, track network issues, and keep your system running correctly after file system problems.