How to run sfc /scannow in Windows 11 and 10 (and read the results)

Applies to: Windows 11 and Windows 10 (the same commands work on Windows 8.1).

How to run sfc /scannow

SFC (System File Checker) only works from an elevated window. Running it in a normal one gives the message “You must be an administrator running a console session in order to use the sfc utility.”

1. Click Start, type cmd, right-click Command Prompt and choose Run as administrator. On Windows 11 you can also press Win + X and choose Terminal (Admin).
2. Click Yes in the User Account Control prompt.
3. Type sfc /scannow (note the space before the slash) and press Enter.
4. Wait. The scan usually takes 5 to 20 minutes, longer on a slow hard drive. Don’t close the window.
5. Read the message at the end (see what the result means) and restart if files were repaired.

Run DISM first on Windows 11 and 10

SFC repairs files from a local store of good copies (the component store in C:\Windows\WinSxS). If that store is damaged too, SFC can’t fix anything. Microsoft’s own instructions therefore run DISM before SFC, so DISM can repair the store from Windows Update:

DISM.exe /Online /Cleanup-image /Restorehealth
sfc /scannow

DISM can pause around 20% or 62% for several minutes; that’s normal. It needs an internet connection. If DISM fails with a source error, see error 0x800f081f, which covers repairing from a Windows ISO.

What the result means

• “Windows Resource Protection did not find any integrity violations.” Your system files are fine. The problem you’re chasing lies elsewhere, such as a driver, an app or the hardware.
• “Windows Resource Protection found corrupt files and successfully repaired them.” Restart the PC, then run sfc /scannow once more to confirm it now comes back clean.
• “Windows Resource Protection found corrupt files but was unable to fix some of them.” Run the DISM command above, restart, and run SFC again. If it still fails, check the log to see which files are affected, or run SFC from outside Windows with SFC offline.
• “Windows Resource Protection could not perform the requested operation.” Something blocked the scan, often pending repairs or disk errors. Follow this guide to the “could not perform the requested operation” error.
• “Windows Resource Protection could not start the repair service.” The Windows Modules Installer service is disabled. See if SFC won’t start.

See which files SFC repaired

SFC writes its results to C:\Windows\Logs\CBS\CBS.log, which also holds a lot of unrelated Windows Update entries. To pull out only the SFC lines into a text file on your desktop, run this in the same admin window:

findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"%userprofile%\Desktop\sfcdetails.txt"

Open sfcdetails.txt and look for lines that say Cannot repair member file. They name the files SFC couldn’t replace, which helps if you need to search for that specific file or ask for support.

If SFC won’t start or gets stuck

• “Could not start the repair service”: run sc config trustedinstaller start= demand and then net start trustedinstaller (the space after start= is required), then run SFC again.
• Stuck at a percentage: give it at least 30 minutes, especially on a hard drive. If it truly doesn’t move, restart and try again in Safe Mode, where fewer programs can interfere.
• Windows won’t start at all: boot into Windows Recovery and run the offline version described in SFC offline.
• It keeps finding new corruption: repeated damage often points to a failing drive or bad RAM. Check the drive’s health and run Windows Memory Diagnostic (mdsched.exe).

Other SFC options

• sfc /verifyonly checks files but doesn’t repair them.
• sfc /scanfile=C:\Windows\System32\filename.dll checks and repairs one file (use the full path).
• sfc /verifyfile=C:\Windows\System32\filename.dll checks one file without repairing it.
• sfc /scannow /offbootdir=D:\ /offwindir=D:\Windows scans an offline Windows installation; the drive letter is usually different in recovery.

Related guides

• SFC offline: how to run sfc /scannow from recovery
• Windows Resource Protection could not perform the requested operation
• Error 0x800f081f: fix DISM and .NET Framework source errors
• Error 0xc0000005 on Windows: what it means and how to fix it
• How to open Command Prompt as administrator

Official sources: for more detail, see Microsoft’s own pages:

• Microsoft Support: Use the System File Checker tool to repair missing or corrupted system files
• Microsoft Learn: sfc command reference

Frequently asked questions

Is it safe to run sfc /scannow?

Yes. It only replaces protected Windows system files with Microsoft’s own copies and doesn’t touch your documents, photos or installed apps.

Should I run SFC or DISM first?

On Windows 10 and 11, run DISM first, then SFC. DISM repairs the source that SFC copies good files from.

How often should I run sfc /scannow?

Only when something is wrong, such as crashes, missing features or errors after a failed update. There’s no benefit in running it on a schedule.

Can I keep using the PC while SFC runs?

Yes, but avoid installing updates or software, and don’t close the window or shut down until it finishes.