Resolved: Unable to Enable Windows Defender – 2025

Resolved: Unable to Enable Windows Defender

Windows Defender is a crucial part of your system’s built-in security. When it refuses to turn on, your device could be left vulnerable to malware, spyware, and other threats. Fortunately, there are several proven solutions that can help you get Windows Defender working again.

WHY WINDOWS DEFENDER WON’T TURN ON

Before jumping into the fixes, it’s important to understand the possible causes:

• Third-party antivirus software: These often disable Windows Defender automatically.
• Corrupted system files: Essential system files might be damaged.
• Group Policy settings: In some cases, Defender is disabled through policy settings.
• Windows Update issues: Outdated or incomplete updates can prevent Defender from running.

1. UNINSTALL THIRD-PARTY ANTIVIRUS SOFTWARE

If you’re running another antivirus program, it may be preventing Windows Defender from starting. To fix this:

• Go to Settings > Apps > Apps & Features.
• Locate your antivirus and click Uninstall.
• Restart your computer.
• Try enabling Windows Defender again.

2. ENABLE WINDOWS DEFENDER USING WINDOWS SECURITY SETTINGS

• Open Settings > Update & Security > Windows Security.
• Click Virus & threat protection.
• Click Manage settings under Virus & threat protection settings.
• Make sure Real-time protection is turned on.

3. ENABLE WINDOWS DEFENDER USING GROUP POLICY EDITOR

For Windows 10 Pro or Enterprise users:

• Press Win + R, type gpedit.msc, and press Enter.
• Navigate to: Computer Configuration > Administrative Templates > Windows Components > Windows Defender Antivirus.
• Double-click Turn off Windows Defender Antivirus.
• Set it to Disabled or Not Configured.
• Click Apply, then OK.
• Restart your PC.

4. USE THE REGISTRY EDITOR TO ENABLE DEFENDER

Warning: Editing the registry can be risky. Make sure to back up the registry first.

• Press Win + R, type regedit, and press Enter.
• Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender
• Find the DisableAntiSpyware entry.
• If it exists and is set to 1, double-click and change it to 0.
• Close the editor and restart your computer.

5. CHECK FOR WINDOWS UPDATES

Missing or incomplete updates might be the issue:

• Go to Settings > Update & Security > Windows Update.
• Click Check for updates.
• Install any available updates.
• Restart your PC.

6. RUN A SYSTEM FILE CHECK (SFC)

Corrupted system files can prevent Defender from working:

• Open Command Prompt as Administrator.
• Type sfc /scannow and press Enter.
• Wait for the process to complete.
• Restart your system.

7. USE THE WINDOWS DEFENDER SERVICE MANAGER

Make sure the required services are running:

• Press Win + R, type services.msc, and press Enter.
• Locate Windows Defender Antivirus Service.
• Right-click and select Start (if it’s stopped).
• Also ensure Security Center and Windows Defender Advanced Threat Protection services are running.

8. USE WINDOWS SECURITY TROUBLESHOOTER

• Go to Settings > Update & Security > Troubleshoot.
• Click Additional troubleshooters.
• Select Windows Security, then click Run the troubleshooter.
• Follow the prompts.

9. PERFORM A CLEAN BOOT

A clean boot can help eliminate software conflicts:

• Press Win + R, type msconfig, and press Enter.
• Go to the Services tab.
• Check Hide all Microsoft services, then click Disable all.
• Go to the Startup tab and click Open Task Manager.
• Disable all startup items.
• Restart your computer and try turning on Windows Defender.

10. PERFORM AN IN-PLACE UPGRADE

If all else fails, an in-place upgrade can repair Windows without deleting your files:

• Download the Windows 10 Media Creation Tool from Microsoft.
• Run the tool and choose Upgrade this PC now.
• Follow the on-screen instructions.

FINAL THOUGHTS

Windows Defender is your first line of defense. If it’s not turning on, you’re risking exposure to numerous threats. Try each of these steps in order until you find a solution that works. If the issue persists even after trying everything, you may want to consider reaching out to Microsoft Support or performing a full system reset.

Let us know which fix worked for you!