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What is the SFC scanner in Windows and how it works

SFC scanner

If you’ve ever read more than one article about fixing a certain issue in Windows, you’ve probably noticed that a lot of them mention the SFC scanner as one of the solutions. Now, you know this tool has something to do with fixing some issues on your computer, but that’s all you know about it.

You’re not sure what the SFC scanner does precisely, nor what are the issues it fixes. That’s why we’re here, to help you understand this popular troubleshooting feature.

The SFC scanner is a built-in utility, integral to the Windows operating system, which offers a lifeline by scanning for and repairing corrupted or missing system files. Whether you’re battling unexpected system errors, performance dips, or mysterious software crashes, understanding how to leverage the SFC scan can be your first step toward resolution.

So, let’s explore it further.

1. What’s the purpose of the SFC scanner

The primary purpose of the SFC scan is to ensure that all Windows system files are present, genuine, and functioning properly. System files can become corrupted over time for a variety of reasons, including unexpected shutdowns, malware infection, and software installation conflicts. When these files are corrupted, your system may behave unexpectedly or even crash.

By verifying and restoring the integrity of critical system files, the SFC scan helps to prevent system instability and crashes caused by corrupted or missing system files. This stability is critical for both personal and professional use, as unexpected downtime can result in productivity loss or data loss.

Corrupted system files can cause your computer to run slowly, generate application errors, or exhibit erratic system behavior. The SFC scan ensures that system files are functioning properly, which contributes to better overall system performance.

How the SFC scanner works

The SFC scan works by scanning all protected system files and verifying their integrity. If it discovers any missing, corrupted, or tampered files, it attempts to resolve the issue by replacing the problematic files with a cached copy located in a compressed folder at%WinDir%\System32\dllcache (where%WinDir% is the Windows directory, typically C:\Windows on most systems).

To run an SFC scan, you need to open the Command Prompt as an administrator. Here’s how you can do it:

  1. Search for Command Prompt in the Start menu, right-click on it, and select Run as administrator.
  2. Once the Command Prompt opens, type the following command and press Enter: sfc/scannow. What is the SFC scanner in Windows and how it works
  3. The scan will start, and it may take some time to complete (usually from a few minutes to about half an hour, depending on your system’s performance and the extent of the issues). During this process, it’s best not to use your computer for other tasks.

2. After the Scan

Once you complete the SFC scan:

  • If issues are found and fixed, you may be prompted to restart your computer. It’s important to follow this instruction to ensure that all changes take effect.
  • If no issues are found, it means your system files are in good shape, and the problems you’re experiencing might be related to something else.
  • In some cases, the SFC scan might not be able to fix all issues. If this happens, you might need to explore other repair options, such as the DISM (Deployment Image Service and Management Tool) command or a Windows repair installation.

3. The SFC scan limitations

While powerful, the SFC scan is not a panacea. It specifically targets system file integrity and won’t solve all types of computer problems. For issues unrelated to Windows system files, such as third-party software errors or hardware failures, other troubleshooting steps will be necessary.

On top of that, while the SFC scan can repair system files modified by malware, it does not detect or remove the malware itself. A dedicated antivirus or anti-malware tool is necessary to cleanse an infected system thoroughly.

The SFC scan relies on a local cache of system files (stored in %WinDir%\System32\dllcache) to replace corrupted files. If this cache is corrupted or if specific files are not available in the cache, the SFC might not be able to perform the necessary repairs.

All in all, the System File Checker (SFC) scan is more than just a utility; it is essential for maintaining a stable Windows operating system. The SFC scan is essential for troubleshooting and preventing a wide range of common computer problems because it ensures the integrity and security of system files. Its ability to automatically repair file system corruption makes it an invaluable tool for users of all levels, from IT professionals to everyday users who want to keep their systems in good working order.

While we are on the subject of Windows maintenance, Microsoft offers a tool that might help you address some minor problems. It’s Microsoft PC Manager.

Using the SFC scan as part of your regular maintenance routine can significantly improve your computer’s performance and stability, making it resistant to both internal corruption and external threats.

Aleksandar Ognjanovic

Aleksandar Ognjanovic

Managing editor at Mobile Internist. @lemmingspain My fascination with mobile technology, particularly Android and iOS, began years ago and continues today. I'm captivated by the constant evolution in the smartphone industry and its impact on our daily lives, always anticipating the next big innovation. That’s the main reason why I found myself writing instructive content on the subject for users who are not as familiar with all the bells and whistles.
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