System File Checker (sfc)

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

System File Checker (sfc)

Scans and verifies the versions of all protected system files after you restart your computer.


sfc[/scannow] [/scanonce] [/scanboot] [/revert] [/purgecache] [/cachesize=x]

  • /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.
  • /revert
    Returns the scan to its default operation.
  • /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.
  • /?
    Displays help at the command prompt.
  • You must be logged on as a member of the Administrators group to run sfc.

  • If sfc discovers that a protected file has been overwritten, it retrieves the correct version of the file from the systemroot\system32\dllcache folder, and then replaces the incorrect file.

  • 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.

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Format Meaning


Information that the user must supply


Elements that the user must type exactly as shown

Ellipsis (...)

Parameter that can be repeated several times in a command line

Between brackets ([])

Optional items

Between braces ({}); choices separated by pipe (|). Example: {even|odd}

Set of choices from which the user must choose only one

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Code or program output

See Also


Driver signing for Windows
Command-line reference A-Z
Command shell overview