What an installer integrity check does and when you need one

An installer integrity check verifies that your Windows 11 system files have not been damaged, deleted, or altered since installation. Windows includes two built-in tools that scan for these problems: the System File Checker (SFC) and the Deployment Image Servicing and Management tool (DISM). Both run from your command line and report what they find.

You should run an integrity check if Windows is crashing unexpectedly, programs are failing to open, you see error messages about missing files, or your computer is running slowly without an obvious cause. These checks can also help after a failed update or if malware has been removed and left damage behind.

The process takes 15 to 45 minutes depending on which tool you use and how many files need repair. Your computer will remain usable during the scan, though it may run slower. You need administrator access to run either tool.

Key Takeaways

  • The System File Checker (SFC) scans Windows system files and repairs corrupted ones automatically, and you run it by typing a single command in Command Prompt.
  • DISM is a more thorough tool that checks the Windows image itself and can fix problems SFC cannot, but it requires an internet connection to download replacement files.
  • You must open Command Prompt as administrator — right-click the Command Prompt icon and select "Run as administrator" — or the scan will not work.
  • If SFC finds problems but cannot repair them, run DISM next, as it can often fix what SFC leaves behind.
  • After either scan completes, restart your computer so Windows can finish any repairs that require a reboot.

Running the System File Checker scan

The System File Checker is the faster of the two tools and should be your first step. Open the Start menu, type "Command Prompt" in the search box, right-click the result, and select "Run as administrator". Windows will ask for permission — click "Yes".

In the Command Prompt window, type exactly this: sfc /scannow and press Enter. The scan will begin immediately. You will see a progress bar that moves from 0% to 100%. This usually takes 15 to 30 minutes. Do not close the Command Prompt window or restart your computer while the scan is running.

When the scan finishes, you will see one of three messages. "No integrity violations were found" means your system files are intact and you can close Command Prompt. "Windows Resource Protection found corrupt files and successfully repaired them" means problems were fixed — restart your computer and the repairs will complete. "Windows Resource Protection found corrupt files but was unable to fix some of them" means you need to run DISM next.

Running DISM when SFC cannot repair files

DISM (Deployment Image Servicing and Management) is a deeper scan that can fix problems the System File Checker cannot reach. You only need to run it if SFC reported that it found corrupt files but could not repair them. DISM requires an active internet connection because it downloads replacement files from Microsoft's servers.

Open Command Prompt as administrator again using the same method: Start menu, search "Command Prompt", right-click, select "Run as administrator". Type this command exactly: DISM /Online /Cleanup-Image /RestoreHealth and press Enter. This scan takes 20 to 45 minutes and will show a progress percentage as it runs.

When DISM finishes, it will report whether it found and repaired problems. If it reports success, restart your computer. If it reports that it could not repair certain files, those files may require a Windows repair or reinstall, which is beyond what these tools can fix.

What to do if the scan finds nothing but problems persist

If both SFC and DISM report no problems but your computer is still crashing or showing errors, the issue is likely not corrupted system files. The problem could be a failing hard drive, incompatible software, outdated drivers, or malware that was not fully removed.

Run a full malware scan using Windows Defender (built into Windows 11) or a third-party antivirus tool. Check Device Manager for any devices with warning symbols, which indicate driver problems. If your hard drive is making clicking sounds or Windows is reporting disk errors, the drive itself may be failing and needs replacement.

You can also try updating Windows itself: go to Settings, select "Update & Security", and click "Check for updates". Sometimes a newer version of Windows includes fixes for problems that the integrity check cannot address.

Running the checks from Safe Mode if Windows will not start normally

If Windows crashes before you can reach the desktop, you can still run these checks from Safe Mode, which loads only essential drivers and services. Restart your computer and hold down the F8 key repeatedly as it boots. You should see a menu with boot options — select "Safe Mode with Command Prompt".

Once Safe Mode loads, you will see a Command Prompt window already open. Type the SFC command (sfc /scannow) or DISM command (DISM /Online /Cleanup-Image /RestoreHealth) exactly as described above. The scan will run the same way, though it may take slightly longer because Safe Mode has fewer resources available.

If you cannot reach the F8 menu, restart your computer three times in a row by holding the power button for 10 seconds each time. Windows will detect the repeated crashes and automatically boot into recovery mode, where you can access Command Prompt from the "Troubleshoot" menu.

Understanding what each scan result means

When SFC reports "No integrity violations were found", your Windows system files are not the source of your problems. When it reports "successfully repaired them", those repairs are usually complete immediately, though some may require a restart to take effect.

When DISM reports success, it has downloaded and installed replacement files from Microsoft. This is more thorough than SFC because it replaces entire file versions rather than trying to repair individual corrupted files. If DISM reports that it could not repair certain files, those files are likely damaged in a way that requires a full Windows reinstall.

If both tools report success but your problems continue, the issue is not file corruption. Document what error messages you see, what programs are failing, or when the crashes happen, and search for those specific symptoms. A corrupted file in a single program (like Microsoft Office or a game) would not show up in these system-wide scans.

Frequently Asked Questions

Do I need to run both SFC and DISM, or just one?

Start with SFC because it is faster. If it reports that it repaired files, restart and you are done. If it reports that it found files but could not repair them, then run DISM. Running both is not necessary unless SFC specifically says it needs help.

Can I use my computer while the scan is running?

Yes, but the scan will run slower if you are using other programs. Close unnecessary applications and avoid large downloads or video playback while the scan is in progress. The scan needs system resources to work efficiently.

What if the Command Prompt window closes before the scan finishes?

The scan stops immediately. Open Command Prompt as administrator again and run the same command to restart the scan from the beginning. There is no way to resume a scan that was interrupted.

Will these scans delete any of my files or programs?

No. SFC and DISM only repair or replace system files that Windows uses to run. They do not touch your documents, photos, downloads, or installed programs. Your personal files remain exactly as they are.

How often should I run these checks?

Run them only when you notice problems — unexpected crashes, error messages, or programs failing to open. There is no benefit to running them regularly on a computer that is working normally. Running them once a year as preventive maintenance is unnecessary.