how to do sfc?

Regardless of the reason, if you come across any related issues, Windows 10 includes the System File Checker (SFC), a command-line tool designed to scan the integrity and restore missing or corrupted system files with working replacements.

This guide will walk you through the steps to use the System File Checker tool to repair damaged system files automatically or manually on Windows 10.

Warning: This is a friendly reminder that editing a system file is risky and can cause irreversible damage to your installation if you don't do it correctly. It is recommended to make a temporary full backup of your PC before proceeding.

To repair an installation of Windows 10 using the System File Checker tool, use these steps:

Once you complete the steps, the SFC command-line tool will scan, detect, and fix Windows 10 system file problems.

When the tool detects an issue, it is recommended to run the command around three times to ensure that all the problems have been corrected properly.

If you find problems running the tool, use this guide to use the Deployment Image Servicing and Management (DISM) tool to repair the local Windows 10 image files to allow SFC to complete successfully.

System File Checker logs

To view the details stored in the CBS.Log file from an SFC scan, use these steps:

After you complete the steps, the log file will reveal all the scanned system files and information for the unrepairable files.

This option is only available when performing a scan within Windows 10, not when performing an offline scan with Command Prompt.

To repair Windows 10 using SFC with the offline option, use these steps:

In the command, we are using the /offboodir option to specify the drive letter of the System Reserved partition, which in this case is F. Also, the /offwindir option specifies the location of the Windows 10 files, which in this case is C:\Windows.

Once you complete the steps, the tool will fix problems with system files, and the device will start normally.

If the System File Checker cannot fix the damaged files, you may need to repair them manually.

Determine corrupted system files

To find out which files need replacing on Windows 10, use these steps:

After you complete the steps, the log file will reveal all the scanned system files and information for files that could not be repaired.

While in the file, you can use the find option (Ctrl + F) in the text editor and look for the term: "Cannot repair member file" to identify the corrupted files that need replacing.

Repair system files manually

You may be able to get good working files to replace your installation from another computer running the exact edition and version of Windows 10. If you do not know the location of the damaged file, you may need to perform an online search with the information in the SFC log file.

To repair damaged system files on Windows 10 manually, use these steps:

In the command, replace C:\PATH\TO\FILE with the actual path to the file that you are trying to fix. This example takes ownership of the "acproxy.dll" file: takeown /f C:\Windows\System32\acproxy.dll

In the command, replace C:\PATH\TO\FILE with the actual path to the file you are trying to fix. This example grants access to the "acproxy.dll" file: icacls C:\Windows\System32\acproxy.dll /Grant Administrators:F

In the command, replace C:\PATH\TO\SOURCE\GOOD\FILE with the path of the new file and C:\PATH\TO\DESTINATION\BROKEN\FILE with the path of the corrupted file.

In the command, replace C:\PATH\TO\REPLACED\FILE with the path of the file you replaced. This example verifies the integrity of the "acproxy.dll" file inside the System32 folder: sfc /verifyfile=C:\Windows\System32\acproxy.dll

Once you complete the steps, if the new files pass the integrity check, you have resolved the problems with Windows 10.

If you cannot repair the installation using the System File Checker, you may consider starting fresh with a clean installation of Windows 10.

For more helpful articles, coverage, and answers to common questions about Windows 10 and Windows 11, visit the following resources:

The SFC (System File Checker) command is a Command Prompt command that is used to verify and replace important Windows system files. There are several specific switches available in the SFC command such as:

Among all the command switches, sfc /scannow is the most frequently-used one. It is extremely useful to repair incorrect, corrupted, changed, or damaged system files. Then, how to perform sfc /scannow repair exactly?

To run sfc /scannow in Windows 10/11, you can follow the steps below:

1. Tap the Search button on the taskbar and type “cmd” in the search box. Right click “cmd” and then select “Run as administrator”.

2. Type DISM.exe /Online /Cleanup-image /Restorehealth and press Enter. It may take several minutes for the command operation to be completed.

Note: Running the DISM (Deployment Image Servicing and Management) tool prior to SFC is only necessary on Windows 11/10/8.1/8. To run sfc /scannow in Windows 7, you can skip to Step 3.

3. Type sfc /scannow and press Enter to scan system files and replace corrupted files with a cached copy that is located in a compressed folder at %WinDir%\System32\dllcache.

Note: The %WinDir% placeholder represents the Windows operating system folder. For example, C:\Windows.

4. After the verification reaches 100%, you may receive one of the following messages:

▶ Windows Resource Protection did not find any integrity violations. >> A good thing. ▶ Windows Resource Protection found corrupt files and successfully repaired them.  >> A good thing. ▶ Windows Resource Protection found corrupt files but was unable to fix some of them. >> In this case, you can view details of the System File Checker process in %WinDir%\Logs\CBS\CBS.log, and then manually replace the corrupted file with a known good copy of the file. ▶ Windows Resource Protection could not perform the requested operation. >> In this condition, you can perform the System File Checker scan in safe mode, and make sure that the PendingDeletes and PendingRenames folders exist under %WinDir%\WinSxS\Temp.

5. Type exit and press Enter to exit Command Prompt.

Although you can fix corrupted system files with the sfc /scannow command, problems may occur during the process, such as sfc /scannow not working, sfc /scannow stuck, etc. You even need to reinstall Windows to repair damaged system files when sfc /scannow fails. How to get away from the scare of sfc /scannow failure? Please read on.

To be released from the heavy work of reinstalling Windows when sfc /scannow fails, you should backup Windows regularly. Compared with reinstalling Windows and all the applications, restoring system from the backup is much easier. Here I’d like to recommend the best free backup software—AOMEI Backupper Standard.

Learn how to backup Windows on a regular basis via AOMEI Backupper below:

Step 1. Download, install and launch AOMEI Backupper. Click on “Backup” and select “System Backup”.

Step 2. The required system partition(s) is (are) selected by default. Choose the destination path to store the backup files. You can save the system image to the local disk, external hard drive or network location.

Step 3. Click “Schedule Backup” in the left bottom, and then set the frequency of the system backup to run.

Step 4. Confirm the operation and click “Start Backup”.

>> Options: you can enable email notification, choose the compression level for the backup image file and select intelligent sector backup or sector-by-sector backup. >> Backup Scheme: it will automatically remove older backups to save disk space for you. This feature is available in AOMEI Backupper Professional and higher editions.

In the command prompt window, type SFC /scannow and press Enter . System file checker utility checks the integrity of Windows system files and repairs them if required. After the process is complete, reboot the computer.