System File Checker (SFC): How to Scan and Repair Corrupted Windows System Files

Windows includes a built-in System File Checker (SFC) utility that scans protected system files and repairs corrupted or missing files that may cause Windows problems. If Windows shows unexpected errors, built-in features stop working, applications crash, or the system becomes unstable, running SFC /scannow is one of the first repair steps to try. The tool checks the integrity of protected Windows system files and replaces damaged versions when a suitable copy is available. Microsoft supports SFC on both Windows 11 and Windows 10.

In this guide, you’ll learn what System File Checker does, when you should use it, how to run SFC /scannow correctly, what its scan results mean, and what to do if SFC cannot repair some files. We’ll also cover how SFC works with DISM and several other SFC commands that can be useful when troubleshooting specific system-file problems.

What Is System File Checker (SFC)?

System File Checker (SFC) is a built-in Windows command-line utility that checks the integrity of protected Windows system files. If it finds a corrupted or modified file, SFC attempts to replace it with a cached copy stored by Windows. It supports both Windows 11 and Windows 10. (Microsoft Learn)

The most commonly used SFC command is:

sfc /scannow

When you run this command, Windows checks protected system files and automatically attempts to repair problems. The scan can take time, so don’t close the Command Prompt window while it is running.

SFC can be useful when Windows starts behaving unexpectedly after an update, software installation, driver change, or system crash. It can also help troubleshoot problems such as Windows features not working correctly or certain applications failing because of damaged system files.

However, SFC is not a general-purpose repair tool for every Windows problem. If SFC cannot repair the corrupted files, Microsoft recommends using the DISM tool to repair the Windows component store and then running SFC again. (Microsoft Support)

Quick insight: Think of SFC as a Windows system-file checker and repair tool—not a disk cleaner, malware scanner, or performance optimizer.

When Should You Run SFC on Windows?

You don’t need to run System File Checker regularly. It is mainly useful when you suspect that Windows system files have become corrupted or damaged.

Consider running SFC if you are experiencing problems such as:

• Windows features or built-in apps suddenly stop working.
• You receive errors related to missing or corrupted system files.
• Windows behaves unexpectedly after an update or system crash.
• Some system functions fail even though Windows itself starts normally.
• Applications or Windows components repeatedly crash because of damaged system files.
• Windows becomes unstable without an obvious hardware-related cause.

SFC is also a useful troubleshooting step before considering more disruptive repair options such as a Windows reset or reinstall.

However, SFC won’t fix every Windows problem. It cannot repair faulty hardware, remove malware, fix every driver issue, or solve problems caused by insufficient storage or incompatible software. If the scan reports it couldn’t repair some files, you may need to repair the Windows component store with DISM, then run SFC again.

How to Run System File Checker (SFC) in Windows

Before running SFC, close any unnecessary programs and save your work. The scan requires an elevated Command Prompt, so open it with administrator privileges.

1. Press Windows + S and search for Command Prompt.
2. Right-click Command Prompt and select Run as administrator.
3. When the User Account Control prompt appears, select Yes.
4. Enter the following command and press Enter:

sfc /scannow

5. Wait for the verification to reach 100%. Do not close the Command Prompt window while the scan is running.
6. When finished, Windows will display a message indicating whether it found and repaired corrupted files.

The /scannow option tells SFC to scan all protected system files and attempt to repair any problems it finds. The scan can take several minutes, depending on your system.

Quick insight: If SFC completes successfully, restart Windows and check whether the original problem has been resolved. If SFC reports that it could not repair some files, don’t keep running the same command repeatedly—move on to the appropriate repair steps below.

What the SFC Scan Results Mean

When SFC finishes, it displays a message explaining whether it found and repaired corrupted system files.

• Windows Resource Protection did not find any integrity violations: SFC found no corruption in the protected system files it checked. If you are still experiencing a Windows problem, the cause may be elsewhere, such as a driver, Windows component, application, or hardware issue.
• Windows Resource Protection found corrupt files and successfully repaired them: SFC found damaged files and repaired them. Restart Windows and check whether the original problem is resolved.
• Windows Resource Protection found corrupt files but was unable to fix some of them: SFC found damaged files but could not repair all of them. In this case, use DISDISM /Online /Cleanup-Image /RestoreHealthM to repair the Windows component store and then run SFC again.
• Windows Resource Protection could not perform the requested operation: SFC could not complete the scan. Running the scan from Safe Mode may help.

The most common result that requires additional troubleshooting is when SFC cannot repair some files. The steps below explain what to do in that situation.

What to Do If SFC Cannot Repair Corrupted Files

If SFC reports that it found corrupted files but could not repair some of them, the next step is usually to repair the Windows component store with DISM. SFC relies on files in this component store when repairing protected system files, so problems with the component store can prevent SFC from completing repairs.

If SFC reports that it found corrupt files but was unable to fix some of them, don’t worry. This usually means the files SFC needs to repair are unavailable or damaged. SFC usually relies on files in this component store to repair protected system files, so problems with the component store can prevent SFC from completing repairs.

Open Command Prompt as administrator and run:

DISM /Online /Cleanup-Image /RestoreHealth

Wait for the operation to reach 100%. It can take several minutes, and the progress may appear to pause at certain percentages.

When DISM finishes successfully, run SFC again:

sfc /scannow

This time, SFC may be able to repair files that it could not fix during the first scan.

Why this works: DISM repairs the Windows component store that SFC relies on when replacing corrupted system files. Microsoft recommends this sequence when SFC cannot complete repairs.

In most cases, the recommended order is:

DISM /Online /Cleanup-Image /RestoreHealth
↓
sfc /scannow

This is particularly useful when SFC repeatedly finds corruption but cannot fix everything.

How Long Does an SFC Scan Take?

An SFC scan usually takes 10 to 20 minutes, although the exact time depends on your PC and the condition of Windows system files.

During the scan, the progress may stay at a certain percentage for a while. This does not necessarily mean SFC has stopped working. Let the scan finish, and don’t close the Command Prompt window while it is running.

If the scan genuinely appears stuck for a long time or repeatedly fails to complete, restart Windows and run the scan again. If the problem continues, running DISM before SFC can help repair the Windows component store and allow SFC to complete successfully.

SFC vs. DISM: What Should You Run First?

SFC and DISM are both built-in Windows repair tools, but they handle different parts of the Windows installation.

• SFC checks and repairs protected Windows system files. It compares these files against a cached copy and replaces corrupted versions when possible.
• DISM repairs the Windows component store, which provides the files and resources that Windows uses for system repairs. If the component store itself is damaged, SFC may not be able to repair all the corrupted files it finds.

For a normal SFC scan, you can start with:

sfc /scannow

If SFC reports that it found corrupted files but was unable to fix some of them, run:

DISM /Online /Cleanup-Image /RestoreHealth

Then run SFC again:

sfc /scannow

You don’t need to choose between the two tools in every situation. SFC is usually the first step for protected system-file corruption, while DISM is useful when the Windows component store needs repair or SFC cannot complete the repair.

A simple way to remember the difference is:

Tool	Main purpose
SFC	Checks and repairs protected Windows system files
DISM	Repairs the Windows component store used by Windows servicing and repair

Using both together can resolve problems that neither tool can fix on its own.

How to Run SFC From Windows Recovery Environment

If SFC cannot complete its scan while Windows is running normally, you can run it from Windows Recovery Environment (WinRE). This helps when Windows has serious system-file problems or cannot boot normally.

1. Open Windows Recovery Environment

You can enter WinRE from Windows 11 or Windows 10 by opening Settings > System > Recovery and selecting Restart now next to Advanced startup.

If Windows cannot start normally, you can also reach the recovery environment through Windows installation or recovery media. (Microsoft support)

2. Open Command Prompt

After the PC restarts, select:

Troubleshoot > Advanced options > Command Prompt

Windows may ask you to select your administrator account and enter its password.

3. Find the Windows Drive Letter

When you are in WinRE, Windows may not use the usual C: drive letter. First, identify which drive contains the Windows installation.

Run:

diskpart

Then:

list volume

Look for the volume containing your Windows installation. You can leave DiskPart by running:

exit

You can then check the drive by entering, for example:

dir C:\Windows

If that folder is not found, try another drive letter such as D: or E:.

4. Run SFC Against the Windows Installation

Once you know the correct Windows drive letter, use the following command, replacing C: if necessary:

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

SFC will scan the offline Windows installation and attempt to repair corrupted protected system files.

After the scan finishes, restart the computer and check whether Windows is working normally again.

Other Useful SFC Commands

Although sfc /scannow is the command most people need, SFC includes several other options that can be useful when troubleshooting specific system-file problems.

sfc /verifyonly

This command checks the integrity of protected Windows system files but does not attempt to repair them.

sfc /verifyonly

It can be useful when you only want to find out whether Windows system files have integrity problems.

sfc /scanfile

You can use this option when you suspect that a particular system file is damaged. Replace the path with the actual file you want to check and repair.

sfc /scanfile=C:\Windows\System32\example.dll

Unlike /scannow, this command focuses on the specified file rather than scanning all protected system files.

sfc /verifyfile

This option checks a specific protected system file without attempting to repair it.

sfc /verifyfile=C:\Windows\System32\example.dll

sfc /?

If you want to see the available SFC options directly in Windows, run:

sfc /?

Windows will display the supported commands and explain what each option does.

For most Windows users, however, sfc /scannow remains the best starting point. The other options are mainly useful for targeted troubleshooting.

How to Check the SFC Log for More Details

When SFC finds corrupted files, Windows records scan information in the CBS.log file. This log helps if SFC says it couldn’t repair some files and you want to identify which files were affected.

SFC records its results in the Windows component servicing log:

C:\Windows\Logs\CBS\CBS.log

However, the CBS log contains information from other Windows servicing operations too, so it can be difficult to read. You can use the following command to extract only the SFC-related entries into a separate text file:

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

After the command finishes, look for SFCDetails.txt on your desktop. Open it in Notepad to see which system files SFC attempted to repair.

This is mainly useful for advanced troubleshooting. If you’re trying to fix a common Windows problem, you usually don’t need to inspect the CBS log unless SFC reports it couldn’t repair some files.

When SFC Doesn’t Fix the Problem

Running SFC can repair corrupted Windows system files, but it cannot fix every Windows problem. If the scan completes successfully and the problem remains, the cause may be elsewhere.

For example, device driver issues, Windows updates, installed applications, malware, storage devices, or hardware usually require different troubleshooting steps.

If SFC reports that it cannot repair some files, try the DISM repair process described above and then run SFC again. If both tools complete successfully but Windows still behaves unexpectedly, avoid running SFC repeatedly. Instead, focus on the specific problem you are experiencing.

For example, if Windows crashes with a blue screen, check the error code and recently installed drivers. If an application keeps crashing, repair or reinstall the application. If Windows becomes slow or freezes, check storage health, available disk space, and other hardware-related causes.

SFC is a useful repair tool, but it isn’t a universal fix for every Windows problem. Knowing what the tool can and cannot repair will help you use it more effectively.

Frequently Asked Questions