System File Checker

System File Checker, Sfc.exe, is a command line utility that scans and verifies the versions of all protected system files after restarting the computer. If System File Checker discovers that a protected file has been overwritten, it retrieves the correct version of the file from the %Systemroot%\System32\Dllcache folder, then replaces the incorrect file.

Syntax

sfc [/scannow] [/scanonce] [/scanboot] [/cancel] [/quiet] [/enable] [/purgecache] [/cachesize=x]

Parameters

/scannow Scans all protected system files immediately.

/scanonce Scans all protected system files once.

/scanboot Scans all protected system files every time the computer is restarted.

/cancel Cancels all pending scans of protected system files.

/quiet Replaces all incorrect file versions without prompting the customer.

/enable Returns Windows File Protection to default operation, prompting the user to restore protected system files when files with incorrect versions are detected.

/purgecache Purges the Windows File Protection file cache and scans all protected system files immediately.

/cachesize=x Sets the size, in MB, of the Windows File Protection file cache.

You must be logged on as an administrator or as a member of the Administrators group to run System File Checker. If the %Systemroot%\System32\Dllcache folder becomes corrupt or unusable, use Sfc /scannow, Sfc /scanonce, or Sfc /scanboot to repair the contents of the Dllcache directory.