Microsoft Defender doesn’t work or turn on

Users reported the issue of Windows Defender or Microsoft Defender not working or not turning on. You should be able to fix this issue with the troubleshooting steps given below.

Microsoft Defender will not turn on

Generally, the issue of Microsoft Defender not working or not turning on is reported after users just bought a new computer and also when users try to switch to Microsoft Defender from a third-party antivirus.

With new computers, the problem is usually because McAfee Antivirus is automatically installed on your device. This can be easily fixed by uninstalling McAfee Antivirus program from your computer.

If you cannot turn on Microsoft Defender even after uninstalling McAfee or any other antivirus program, the problem could be due to leftovers or traces or a previously installed antivirus program still active on the computer.

In certain cases, the problem can also be due to Microsoft Defender being blocked or disabled by malware/virus and other reasons.

Tip: In stubborn cases, the only way to fix this problem is to use the “Reset this PC” option (see the last method below).

1. Remove third-party antivirus programs

By default, Microsoft Defender turns off automatically when it detects that a third-party antivirus program is installed on the computer.

Therefore, all previously installed antivirus programs must be removed from the computer. After that, you should be able to turn on Microsoft Defender protection.

Go to settings > applications > Select the in the right pane Anti-virus software you want to remove and click on it Uninstall.

Uninstall program in Windows 10

Repeat the above steps to uninstall all third-party antivirus versions and modules installed on your computer.

2. Manually enable Microsoft Defender

After removing third-party antivirus programs, you may need to manually enable Microsoft Defender Antivirus protection on your computer.

Go to settings > Updates & Security > select Windows security in the left pane. In the right pane, click Virus and threat protection.

Virus and threat protection option in Windows 10

On the next screen, scroll down and click manage settings Link is under Virus & threat protection settings.

Manage virus and threat protection settings in Windows 10

On the next screen, toggle ON real-time protection.

Enable Microsoft Defender real-time scanning

If you want more protection, you can also turn it on Cloud-delivered protection as available on the same screen.

3. Use Antivirus Program Clean Up Tool

If you are unable to turn on Microsoft Defender even after uninstalling the third-party antivirus, the problem may be because there are still traces of the antivirus on your computer.

To fix this, you can use antivirus software removal tools available on Microsoft support page.

Download the removal tool according to the antivirus program installed on your computer > right click on it Downloaded file and click Execute as administrator Possibility.

Run the Norton Removal Tool as an administrator

Select on the next screen Progressive Option > click Remove only and wait for the tool to remove all traces of the antivirus program from your computer.

4. Download the Windows Security Troubleshooter

Go to Microsoft Windows Security Support page and click Download to download the Windows Security Troubleshooter to your computer.

After downloading the file, open the file and follow the instructions to troubleshoot and fix Windows security issues on your computer.

Windows Security Troubleshooter

Note: You can also download the troubleshooter to an external storage drive and run the troubleshooter from a USB drive to fix problems on your computer.

5. Check the Windows Defender registry

It’s possible that Microsoft Defender was permanently disabled on your computer by the third-party antivirus program that was previously installed on your computer.

Right click on the beginning button and click the To run. In the Run Command window, type regedit and click OK.

Open the registry with the

On the Registry Editor screen, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender. In the right pane, double-click Disable AntiSpyware and change its value data from 1 to 0.

Enable or disable Windows Defender

Note: 1 in the value array Disables Windows Defender and 0 Enables Windows Defender.

After that, restart your computer and see if you can enable Microsoft Defender real-time protection on your computer.

6. Scan PC with Microsoft Safety Scanner

If you still cannot turn on Microsoft Defender’s real-time protection, you should use to scan your computer for malware Microsoft security scanner.

After downloading the file, open the file > select type of scan and click the scan Button. Once the scan is complete, you can see the scan results.

Microsoft Safety Scanner results

You can click View detailed results Option to view detailed scan results below %SYSTEMROOT%\debug\msert.log.

7. Run the SFC scan and DISM tool

Run SFC Scan to eliminate the possibility of corrupting or corrupting system files on your computer.

Type command prompt in the search bar > right click on command prompt and select Execute as administrator Possibility.

Open Run command as administrator

In the command prompt window, type sfc /scan and press the Enter Button.

SFC Scannow command Windows 10

Wait patiently while Windows scans your computer for system file errors and fixes them.

After the SFC scan is complete, enter DISM /Online /Cleanup-Image /RestoreHealth and press the Enter key.

DISM tool Windows command prompt

Wait for the DISM tool to scan your computer for errors and fix them.

After the DISM command has run, restart your computer and see if you can now enable Microsoft Defender antivirus protection on your computer.

8. Reset computer

If the above troubleshooting methods didn’t work, it’s time to reset your computer. This was the only method that worked in our case.

The built-in Reset this PC tool offers the option to remove everything from the computer and reinstall the Windows operating system, as well as the option to leave all your personal files intact and reinstall the Windows operating system.

Go to settings > Updates & Security > Select Restoration the left window. In the right pane, click Getting started Option located in the Reset this PC section.

Reset this PC option in Windows

Select on the next screen keep my files option and follow the on-screen instructions to reset your computer.

Reset these PC options in Windows 10

Once the reset process is complete, go to settings > Updates & Security > select Windows security in the left pane. In the right pane, click Open Windows Security.

Open Windows Security

On the next screen, click on the gear-shaped icon Settings icon in the left pane. In the right pane, click Manage Vendors Link found under “Security Providers”.

Manage Security Providers option in Windows Security

On the next screen you should find Microsoft Defender Antivirus Turned ON.

Microsoft Defender is enabled

If you find that McAfee is protecting your computer (instead of Microsoft Defender), you need to uninstall the McAfee Antivirus program from your computer by following the steps as outlined in the first method (above).

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