This article describes the System File Checker tool (Sfc.exe) that is used with the Windows File Protection (WFP) feature.

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The System File Checker tool gives an administrator the ability to scan all of the protected files to verify their versions. The System File Checker tool also checks and repopulates the %SystemRoot%\System32\Dllcache folder. If the Dllcache folder becomes damaged or unusable, you can use either the sfc /scanonce or sfc /scanboot command to repair the contents of the folder.

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System File Checker Tool Syntax

•	The /scannow command scans all protected system files and replaces incorrect versions with correct Microsoft versions. This command also repopulates the DLLCache folder with the most recent versions of protected files. This requires access to the Windows installation source files and also the installed Service Pack files. You are usually prompted for the location of these files during the scan operation.
•	The /scanonce command scans all protected system files once. This command requires access to the Windows installation source files.
•	The /scanboot command scans all protected system files every time that you start your computer. This command requires access to the Windows installation source files.
•	The /cancel command cancels all pending scans of protected system files.
•	The /enable command enables WFP for normal operation.
•	The /purgecache command purges the file cache and scans all of the protected system files immediately. This command requires access to the Windows installation source files. This command is required after you run the /cachesize=x command.
•	The /cachesize=x command sets the file cache size in megabytes (MB). This command requires a reboot followed by a /purgecache command to adjust the size of the on-disk cache.
•	The /quiet command replaces all incorrect file versions without prompting the user.

For additional information about the WFP feature, click the article number below to view the article in the Microsoft Knowledge Base:

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