How to Fix Microsoft Defender Scan Stuck at 0%

If your Microsoft Defender scan is stuck at 0%, it can look like Windows Security has stopped protecting your PC altogether. The good news is that this problem is often caused by a hung service, pending updates, corrupted system files, or a conflict with another security app, and you can usually fix it without drastic changes.

In this guide, you will learn how to troubleshoot a Microsoft Defender scan stuck at 0% on Windows 10 or Windows 11, using safe steps in the right order.

Why this happens

When Microsoft Defender starts a quick, full, or custom scan, it depends on several Windows components working together. The Windows Security app, Microsoft Defender Antivirus Service, Windows Update, and core system files all need to respond normally. If one of them is stuck or partially disabled, the scan may sit at 0% and never begin.

This can also happen after installing another antivirus, removing one incompletely, or postponing Windows updates for a long time. In some cases, a damaged temporary definition file or a problem with the Security Center service keeps the scan from progressing.

Fix it step by step

1. Restart your PC first.
   Before trying anything advanced, save your work and restart Windows. A reboot clears temporary service hangs and can restart Defender components that failed to load properly. After the restart, open Windows Security > Virus & threat protection and try a quick scan again.
2. Check whether another antivirus is installed.
   Open Settings > Apps and look for third-party antivirus software such as Norton, McAfee, Avast, AVG, Bitdefender, or similar tools. Even if you do not use it actively, an installed antivirus can interfere with Microsoft Defender scanning. If you find one, uninstall it using its official uninstaller if available, then restart your PC and test Defender again.
3. Make sure Windows Security services are running.
   Press Windows + R, type services.msc, and press Enter. Find Security Center and confirm its status is running. Also look for Microsoft Defender Antivirus Service if it appears in the list. If a service is stopped, right-click it and choose Start. If it is already running, right-click and choose Restart where available.
4. Install pending Windows updates.
   Go to Settings > Windows Update and click Check for updates. Install all important updates, including security intelligence and platform updates, then restart. A Microsoft Defender scan stuck at 0% is sometimes resolved by newer Defender engine files delivered through Windows Update.
5. Update Defender definitions manually from Windows Security.
   Open Windows Security > Virus & threat protection > Protection updates. Click Check for updates. Wait for the update to finish, then return to the main screen and run a quick scan. If definitions were damaged or outdated, this can restore normal scan behavior.
6. Run System File Checker and DISM.
   Right-click the Start button and choose Terminal (Admin) or Command Prompt (Admin). Run these commands one at a time:
   sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth
   Let both scans finish completely. These tools repair corrupted Windows files that can stop Windows Security scan tasks from launching correctly. Restart when done.
7. Reset the Windows Security app.
   Go to Settings > Apps > Installed apps (or Apps & features on some systems), find Windows Security, click Advanced options, then choose Repair. If the problem continues, return and choose Reset. This can fix a broken app interface that makes it appear the scan never starts.
8. Try a scan in Safe Mode if normal mode keeps freezing.
   Booting into Safe Mode can help if startup software is interfering with Defender. Open Settings > System > Recovery, then under Advanced startup choose Restart now. From the recovery menu, go to Troubleshoot > Advanced options > Startup Settings > Restart, then choose Safe Mode with Networking. Once logged in, open Windows Security and try a scan again.

⚠️ Safe Mode changes how Windows starts. Make sure you save open files first, and only use Safe Mode for testing if you are comfortable navigating recovery options.

9. Use PowerShell to verify Defender status.
   Open PowerShell as Administrator and run:
   Get-MpComputerStatus
   Check whether real-time protection, antivirus service, and signatures appear normal. If the output shows Defender is disabled by policy or another product, that points to a deeper configuration issue that may need professional help.

If the problem keeps coming back

If Microsoft Defender scans work briefly and then get stuck at 0% again, the most likely causes are a leftover third-party antivirus driver, repeated Windows update failures, or corruption inside your Windows user profile or system image. At that point, it is smart to check Event Viewer, review installed security software, and consider guided remote support so you do not disable protection or remove the wrong components by mistake.

Frequently asked questions

Is my PC unprotected if Microsoft Defender is stuck at 0%?

Not always. A stuck manual scan does not necessarily mean real-time protection is off. Open Windows Security and check whether real-time protection is still enabled. If it is off or unavailable, avoid downloading files or browsing risky sites until the issue is fixed.

Can two antivirus programs cause Defender scans to freeze?

Yes. Running multiple antivirus products at the same time is a common reason for scan failures, high CPU use, and security conflicts. Even a partially uninstalled antivirus can leave behind services or drivers that interfere with Microsoft Defender.

Should I disable Microsoft Defender to fix a stuck scan?

No, not unless a trusted technician specifically walks you through a temporary test. Disabling your security software can leave your PC exposed. It is safer to update Windows, repair system files, and remove conflicting antivirus software first.

Need hands-on help with a Microsoft Defender scan stuck at 0% or other antivirus problems? Call 247TechTeam at 888-549-0702 or request a secure remote session.