What Is System File Checker (SFC) and How to Use It in Windows 10 and 11

If your Windows 11 or Windows 10 PC keeps crashing, shows strange error messages, feels unusually slow, or Windows Update fails repeatedly, the problem may be corrupted or missing system files. The System files are crucial operating system components (like drivers, libraries) that tell a computer how to work. If, for some reason, these files are corrupted or damaged due to power issues, malware, failed updates, or hardware failure, it can cause system instability, crashes, or features to stop working. However, Windows includes a built‑in command‑line tool called System File Checker (SFC) that can scan protected system files and replace incorrect versions with the correct ones.

In this guide, you’ll learn:

• What System File Checker (SFC) is and what it does
• When you should run SFC in Windows 10 and 11
• How to use sfc /scannow and other SFC options step by step
• How to read SFC results and find the CBS.log file
• What to do if SFC cannot fix all corrupted files

What Is System File Checker (SFC)?

System File Checker (SFC) is a built‑in Windows command‑line utility that scans all protected system files and replaces corrupted, missing, or modified files with cached copies stored on your PC.

Key points about SFC:

• It checks important Windows system files that are critical for stability and security.
• It compares them against a known good copy stored in the Windows component store (WinSxS).
• If it detects mismatches, it automatically attempts to repair or replace the problematic files.
• It does not delete your personal files (documents, pictures, etc.).

The main purpose of SFC is to help fix problems caused by corrupted or altered system files, such as:

• Windows features are not working correctly
• Windows Update errors
• Random crashes or freezes
• Blue screen errors related to system components

When Should You Run SFC in Windows 10 or 11?

You should consider running SFC if you notice any of these symptoms:

• Windows 11 or 10 randomly crashes or freezes, especially during normal tasks
• You see blue screen errors (BSOD) that may mention system file problems
• Windows Update fails with error codes after multiple attempts
• Built‑in Windows features or apps stop working correctly (Settings app, Start menu, etc.)
• You suspect malware or unwanted software may have changed system files (after you’ve removed the malware)
• You’ve already tried basic fixes (restarts, driver updates, antivirus scan), and issues persist

SFC is often one of the first tools to try when you suspect your Windows installation is damaged.

How to Use SFC (System File Checker) in Windows 11 and 10

SFC is run from Command Prompt or Windows Terminal with administrator rights.

Step 1: Open Command Prompt or Windows Terminal as Administrator

1. Press Windows key + S and type cmd.
2. Right‑click Command Prompt and select Run as administrator.
   • Or open Windows Terminal (Admin) and use the Command Prompt or PowerShell profile.
3. Click Yes on the User Account Control prompt.

Step 2: Run SFC /scannow

In the elevated command window, type:

sfc /scannow

and press Enter.

What this does:

• Scans all protected system files on your PC.
• Automatically attempts to repair or replace any corrupted, missing or modified files.
• Uses a cached copy of system files from the Windows component store.

This scan may take 10–20 minutes or longer, depending on your system and disk speed. Allow it to reach 100%.

Do not close the window or restart your PC while the scan is running.

Understanding SFC Scan Results

When the sfc /scannow command finishes, you’ll see one of several messages.

1. “Windows Resource Protection did not find any integrity violations.”

This means:

• SFC did not find any corrupted or missing protected system files.
• Your system files are likely not the cause of your problem.

You may need to investigate other causes (drivers, hardware, third‑party software, etc.).

2. “Windows Resource Protection found corrupt files and successfully repaired them.”

This means:

• SFC found problems with some system files and repaired them.
• You should restart your PC and see if the issue is resolved.

3. “Windows Resource Protection found corrupt files but was unable to fix some of them.”

This means:

• SFC detected corrupted files but could not repair all of them.
• In this case, you should:
  1. Run SFC again (sometimes multiple passes help).
  2. If the message persists, use DISM /RestoreHealth to repair the Windows image, then run SFC again.

For detailed steps on what to do when you see this message, including DISM commands, Safe Mode, and offline SFC, see: SFC Utility Unable to Fix Corrupted System Files (Windows 10/11).

4. “Windows Resource Protection could not perform the requested operation.”

This usually indicates a deeper problem with the system image or file system.

Possible causes include:

• File system errors
• Pending operations or locks on system files
• Serious corruption in the Windows component store

In this case:

• Run CHKDSK on your system drive to fix disk/file system errors.
• Try running SFC in Safe Mode.
• If that still fails, use DISM /RestoreHealth and then run SFC again.

Other Useful SFC Commands

SFC /verifyonly – Scan Without Repair

If you only want to check for integrity violations without changing anything, use:

sfc /verifyonly

This scans protected system files and reports if any problems are found, but does not attempt repairs.

Running SFC in Safe Mode

If SFC keeps failing or your system is unstable, it can be helpful to run SFC from Safe Mode.

• Boot Windows 10/11 into Safe Mode (press Shift while clicking Restart, then Troubleshoot > Advanced options > Startup Settings > Restart, then press 4 or 5).

• Open Command Prompt (Admin) or Windows Terminal (Admin).
• Run:

  sfc /scannow
  

In Safe Mode, fewer processes and drivers are running, which can reduce interference.

Running SFC Offline from Recovery Environment (Advanced)

If Windows won’t boot or SFC cannot run properly in normal mode, you can run SFC from the Windows Recovery Environment.

• Boot from a Windows 10/11 installation media or use Advanced Startup options.
• Go to Troubleshoot > Advanced options > Command Prompt.

• Identify your Windows drive letter in this environment (it may not be C:).
• Use:

  sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows
  

Replace C:\ with the appropriate drive letter if your Windows installation is on another partition.

This runs SFC against the offline Windows installation.

Where Are SFC Logs Stored? (CBS.log)

SFC logs its detailed actions, and you can find the log file named CBS.log.

• Path:
  C:\Windows\Logs\CBS\CBS.log

This file can be large and difficult to read, but advanced users and technicians can:

• Open it in Notepad or another text editor.
• Search for “[SR]” entries to see specific SFC operations and which files were repaired or could not be repaired.

You can also extract SFC‑related entries to a separate text file, for example:

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

Note: After the scan finishes, type the following command (all on one line) and press Enter to copy relevant log entries to a new file on your desktop:
This command creates a file called sfcdetails.txt on your desktop containing only SFC‑related log lines.

What to Do If SFC Cannot Repair Corrupted System Files

If SFC reports that it found corrupt files but was unable to fix some of them, or you receive errors while running SFC, you’ll need to use other tools.

Typical next steps:

Run DISM /RestoreHealth to repair the Windows image:

DISM /Online /Cleanup-Image /RestoreHealth

• This command repairs the component store (WinSxS), which SFC uses as a source.
• After DISM completes, run sfc /scannow again.

For a full explanation of DISM /CheckHealth, /ScanHealth, /RestoreHealth and using a local source, see: What Is DISM /RestoreHealth in Windows 11 (and 10)? Complete Guide.

Run SFC again after DISM

Sometimes you need to run SFC twice after DISM repairs the image.
Check disk health with CHKDSK

If disk errors are causing repeated corruption, run:

chkdsk C: /f /r

Then restart and allow CHKDSK to complete.

Use Safe Mode or offline SFC

Run SFC in Safe Mode or from the recovery environment if normal mode keeps failing.
Use System Restore or Reset this PC (last resort)

If SFC and DISM cannot repair the system, consider using System Restore to roll back to a working state or Reset this PC to reinstall Windows.

Frequently Asked Questions

Does SFC delete my personal files?
No. SFC only scans and repairs protected Windows system files. It does not delete or modify your personal documents, photos, videos, or other user data.

How often should I run SFC?
You don’t need to run SFC regularly like a maintenance tool. Use it when you:

• Suspect system file corruption (crashes, BSODs, broken Windows features).
• Have problems that persist after updates or driver changes.
• Have just removed malware that might have modified system files.

Is SFC safe to run on SSDs?
Yes. SFC verifies system files and replaces corrupted ones; it doesn’t perform low‑level surface scans like /r in CHKDSK. It is safe on both HDDs and SSDs.

What’s the difference between SFC and CHKDSK?

• SFC checks and repairs Windows system files stored on the disk.
• CHKDSK checks the disk itself and the file system for errors (bad sectors, cross‑linked files, etc.).

They solve different types of problems and are often used together when troubleshooting.

What’s the difference between SFC and DISM?

• SFC verifies and repairs protected system files using the component store as a source.
• DISM /RestoreHealth repairs the component store (Windows image) itself.

If the component store is corrupted, SFC may fail until DISM fixes the image. A common order is:

1. Run DISM /Online /Cleanup-Image /RestoreHealth.
2. Then run sfc /scannow.
3. Restart and test.