How to use Windows 10’s System File Checker (SFC) scannow command to fix problems
If corrupted system files are causing problems on Windows 10, this guide will help you fix this issue with the System File Checker tool.
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On Windows 10, when you notice issues starting yourlaptop, random errors occur, or features don’t work correctly, there is a good chance that some system files might be corrupted or missing for unknown reasons. Usually, you may experience problems with system files after installing a cumulative update or driver or making installation changes manually.
Regardless of the reason, if you come across any related issues,Windows 10includes the System File Checker (SFC), a command-line tool designed to scan the integrity and restore missing or corrupted system files with working replacements.
Thisguidewill 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.
How to repair Windows 10 from System File Checker
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.
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If you find problems running the tool,use this DISM command tool guideto use the Deployment Image Servicing and Management 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.
How to repair Windows 10 from System File Checker offline
To repair Windows 10 using SFC with the offline option, use these steps:
In the command, we are using the/offboodiroption to specify the drive letter of the System Reserved partition, which in this case isF. Also, the/offwindiroption specifies the location of the Windows 10 files, which in this case isC:\Windows.
Once you complete the steps, the tool will fix problems with system files, and the device will start normally.
How to repair Windows 10 manually without System File Checker
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, replaceC:\PATH\TO\FILEwith 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, replaceC:\PATH\TO\FILEwith 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, replaceC:\PATH\TO\SOURCE\GOOD\FILEwith the path of the new file andC:\PATH\TO\DESTINATION\BROKEN\FILEwith the path of the corrupted file.
In the command, replaceC:\PATH\TO\REPLACED\FILEwith the path of the file you replaced. This example verifies the integrity of the “acproxy.dll” file inside theSystem32folder: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 aclean installation of Windows 10.
More resources
For more helpful articles, coverage, and answers to common questions about Windows 10 and Windows 11, visit the following resources:
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Mauro Huculak has been a Windows How-To Expert contributor for WindowsCentral.com for nearly a decade and has over 15 years of experience writing comprehensive guides. He also has an IT background and has achieved different professional certifications from Microsoft, Cisco, VMware, and CompTIA. He has been recognized as a Microsoft MVP for many years.
