Struggling with Windows errors? Understand the crucial difference in Scannow vs DISM. Learn when to use SFC /scannow vs DISM /RestoreHealth for effective system repair.
In fact, Windows is a vast collection of files and components working in concert. Sometimes, those files get corrupted—maybe from a sudden power loss, a dodgy piece of software, or a bungled update. That's when things go haywire.
Thankfully, Windows includes built-in repair utilities: System File Checker (SFC) and the Deployment Image Servicing and Management tool (DISM). The core question of "sfc scannow vs dism restorehealth" revolves around their different levels of operation. Understanding this hierarchy is the first step to effective troubleshooting.
Knowing the differences between SFC scannow and DISM, which tool to use, and when is the key to solving your problem. We'll break down exactly what these tools do, use DISM or SFC first, and provide a step-by-step guide to get your PC running smoothly again.
SFC (System File Checker) and DISM (Deployment Image Servicing and Management) are command-line tools in Windows used to repair corrupted system files and fix operating system instability.
DISM repairs the underlying Windows image (component store), while SFC restores individual corrupted files using that image. It is highly recommended to run DISM first, followed by SFC, to ensure a successful repair.
The comparison between SFC and DISM is not about choosing a superior tool. They are complementary utilities with distinct functions.
SFC (System File Checker) operates as a local integrity scanner. It examines your current system files against a protected, local cache of known-good versions. If it finds a damaged or incorrect file, it replaces it directly from this local cache.
DISM (Deployment Image Servicing and Management) serves as a foundational repair tool. Its primary role is to ensure the health of that local cache—the source SFC depends on. If the cache itself is corrupted or incomplete, SFC cannot function properly. DISM fixes this by repairing the underlying Windows system image, often by downloading clean files directly from Microsoft's servers.
The critical task is to diagnose which layer is compromised—the runtime files (addressed by SFC) or the foundational system image (repaired by DISM).
The System File Checker, invoked by the command sfc /scannow, is your first choice for Windows issues. It's designed to scan all protected system files and verify their integrity. If it finds a file that has been modified, corrupted, or is just plain missing, it automatically replaces it with the correct version from a compressed folder stored locally on your machine, called the DLLCache.
It’s easy to run the SFC commands:
1. Input cmd in the Windows search box, right-click it, and choose Run as an Administrator.
2. Type sfc /scannow, and hit Enter.
The process can take a while (10 to 30 minutes) because it checks thousands of files. You'll see a percentage counter as it works.
3. When it finishes, it gives you one of three results:
It's a localized repair; it doesn't need an internet connection because it relies on that local cache.
SFC is brilliant for solving a host of common, surface-level glitches. If you're experiencing strange application crashes, odd error dialog boxes that won't go away, or features in Windows Settings that seem broken, SFC might be your cure. It's particularly good at fixing issues where a single file has been accidentally overwritten.
However, if the problem is more profound—like a failed Windows Update (think of errors like 0x800f0922) or if SFC itself reports it cannot repair files—you've likely hit the limit of its capability. That's your signal that the local source files SFC depends on are compromised.
DISM (DISM /Online /Cleanup-Image /RestoreHealth) is a tool that repairs the foundational Windows Component Store (WinSxS folder). This store serves as the core source for all system operations and updates. While SFC fixes individual system files in use, DISM services this entire folder.
The command DISM /Online /Cleanup-Image /RestoreHealth instructs DISM to examine your running Windows installation, clean up the component store, and restore its integrity. It typically connects to Windows Update to download correct versions of any corrupted files, though it can also use a local Windows ISO file as a source. Its primary function is not to repair the files currently in use, but to fix the source repository from which tools like SFC and Windows Installer retrieve files.
You should run DISM when SFC cannot repair files, when experiencing persistent Windows Update failures, or before a major system upgrade.
If Windows Update is stuck or generating errors, a corrupted component store is often the cause. Running DISM first restores this foundational layer, enabling SFC and Windows Update to proceed correctly. It is essential preparation.
Therefore, when addressing persistent issues, running DISM before SFC is a critical sequence.
Follow this essential rule for nearly all repair scenarios: Run DISM before SFC. The reason is that SFC relies on the local component store for replacement files—the same store that DISM repairs. If that store is corrupted, SFC cannot source good files and will fail. Running DISM first restores the integrity of this repository, ensuring the supply of correct system files. Afterwards, SFC can effectively use these healthy files to repair the active operating system.
Here is the recommended repair procedure:
1. Open Command Prompt as Administrator.
2. Run DISM: Enter the command DISM /Online /Cleanup-Image /RestoreHealth and press Enter. Allow the process to complete without interruption. It requires an internet connection and may take 10-20 minutes.
3. Run SFC: After DISM finishes successfully, enter the command sfc /scannow and press Enter.
4. Restart: Once SFC completes its scan, restart your computer.
Executing DISM followed by SFC in this order resolves most system file corruption issues.
Here are common situations where both tools are used effectively.
1. Resolve Update and Installer Failures
This is one of the most frequent and important applications. Errors such as "Windows Update failed to install" or failures during installation of the .NET Framework or Cumulative Updates often indicate system corruption. Since the update process depends on the Component Store, running DISM followed by SFC repairs that store and the system files. This often allows the update to install successfully on the next attempt.
2. Apply the Repair Process
For example, if you encounter a generic "installation error" when installing new software or a Windows feature, system file corruption could be the cause. Running DISM and then SFC addresses a common category of underlying Windows problems, turning an unclear failure into one that can often be resolved. This approach systematically repairs the foundation that the installer requires.
In some cases, the standard repair command may not succeed. What are the next steps?
If DISM /Online /Cleanup-Image /RestoreHealth fails—often due to being unable to connect to Windows Update—you can direct it to a local source instead.
First, mount a Windows ISO file to a drive (for example, D:).
Then, run the following command:
DISM /Online /Cleanup-Image /RestoreHealth /Source:D:\sources\install.esd /LimitAccess
Replace D: with your actual drive letter, and install.esd with install.wim if needed. This instructs DISM to use the clean files from your ISO instead of downloading them.
Occasionally, system corruption is too severe for DISM and SFC to resolve. If DISM consistently fails, the final in-place recovery option is a Repair Install. Using the Windows Media Creation Tool, you can perform an in-place upgrade that reinstalls Windows while preserving your personal files, settings, and most applications. This process effectively replaces the entire system image.
What is the main difference between SFC /scannow and DISM /RestoreHealth?
SFC fixes the running Windows system using a local cache. DISM repairs the Windows Component Store, which is the source SFC and Windows Update rely on. SFC addresses active system corruption, while DISM fixes the underlying repository.
Should I run DISM or SFC first? What is the correct order?
Run DISM before SFC. SFC needs the Component Store (which DISM repairs) to be healthy in order to get working replacement files. The standard sequence is: 1. DISM /Online /Cleanup-Image /RestoreHealth, 2. sfc /scannow, 3. Restart.
Can running SFC or DISM harm my computer or delete my files?
No. These tools only repair protected Windows system files. They will not delete your personal documents, photos, or other data.
How long do SFC and DISM scans take to complete?
SFC typically takes 10–30 minutes. DISM often takes 15–45 minutes or longer, as it may download files. Do not interrupt either process.
What does it mean if SFC says "Windows Resource Protection found corrupt files but was unable to fix some of them"?
This means the local cache is damaged. Run DISM to repair the source, then run SFC again. SFC will usually succeed on the second try.
Do I need an internet connection to run DISM /RestoreHealth?
By default, yes—DISM downloads files from Windows Update. Offline, you can point it to a Windows ISO. SFC does not require the internet.
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