</>PC Utility Hub

System File Checker (SFC)

Download System File Checker

System File Checker is a built-in Windows utility that scans protected system files for corruption and replaces damaged copies automatically. This page is the reference for what the tool does, when to use it, and how it fits with DISM.

Updated August 9, 2026 · PC Utility Hub Editorial Team

What System File Checker does

System File Checker (SFC) is a command-line tool built into every version of Windows since Windows XP. It compares the protected system files on your PC against a cached, known-good copy stored by Windows and repairs or replaces any file that has been corrupted, deleted, or overwritten by a bad install or malware.

It runs from an elevated Command Prompt or PowerShell window and does not require any download — the tool and its verification database ship with Windows itself.

Core commands

sfc /scannow scans all protected files and repairs any it can. sfc /verifyonly checks files without making changes, useful for diagnosing an issue before touching anything. The /offbootdir and /offwindir switches let you run SFC against an offline Windows installation, for example when booted from a recovery drive and the OS drive is mounted as D:.

sfc /scannow
sfc /verifyonly
sfc /scanfile=C:\Windows\System32\kernel32.dll
sfc /offbootdir=D:\ /offwindir=D:\Windows

How to run it

  1. 1Press Start, type cmd, right-click Command Prompt and choose Run as administrator.
  2. 2Type sfc /scannow and press Enter.
  3. 3Wait for the scan to reach 100% — this can take 10-20 minutes.
  4. 4Read the result: no violations found, repaired successfully, or unable to fix some files.
  5. 5Restart the PC even if no issues were found, then re-check the problem that prompted the scan.

When SFC can't fix everything

SFC relies on a local component store (WinSxS) for replacement files. If that store is itself damaged, SFC reports that it found corrupt files but could not fix some of them. In that case run DISM /RestoreHealth first to repair the component store, then run SFC again.

Always run DISM before SFC if SFC has already failed once — DISM repairs the source SFC pulls from.

Reading the log

SFC writes details to C:\Windows\Logs\CBS\CBS.log. Filter it with findstr to see only SFC-related lines:

findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log > %userprofile%\Desktop\sfcdetails.txt

Get System File Checker

Start the download and follow the setup steps described on this page.

Download now

Frequently asked questions

Does SFC need internet access?
No. SFC repairs files from the local WinSxS component cache, not from the internet.
Is sfc /scannow safe?
Yes, it is a read/repair operation on system files only and does not touch personal data.
How long does sfc /scannow take?
Typically 10-20 minutes depending on drive speed and system size.
What if SFC finds errors it can't fix?
Run DISM /Online /Cleanup-Image /RestoreHealth, then run sfc /scannow again.

Related pages