[13 Ways] How to Fix Windows Defender Won’t Turn On

Windows Defender is a default antivirus program that comes preloaded in almost all the versions of Windows. It offers real-time protection from various threats such as adware, spyware, and virus. But recently a lot of users have been reporting that they are unable to turn on their Windows Defender. In this guide, I will show 13 different ways to fix Windows Defender when it won’t turn on.

Use antivirus specific removal tools

When you uninstall third-party antivirus solutions using the Uninstall option from the Control Panel, it’s possible that some files remain undetected and this prevents you from running Windows Defender.

Using the Uninstall option from the Control Panel, it is possible that some files won’t get deleted and are still present in your PC. These files can sometimes prevent you from running the Windows Defender. 

Here is a list of antivirus removal tools that you can use to remove the antivirus. In addition to that, you need to also use the uninstaller software. 

If you are not familiar with what uninstaller software is, it is an application that can remove all the junk or hidden files from your PC. The software which I prefer is Systweak’s Advanced System Optimizer, it can remove all the junk files and registry entries associated with an application. This tool is very simple to use.

Check your system files

For this, you can use the System File Checker tool which can repair the corrupted system files on your computer. You can use this tool to verify whether the Windows Defender is corrupted or not. To perform an SFC scan: 

  •  Press the Windows button and type CMD. Now open the CMD with Admin rights.
  • Type the command sfc /scannow and hit enter. Now it will take some time to complete the scan. It will now display if any file is broken.
 Press the Windows button and type CMD. Now open the CMD with Admin rights.
Type the command sfc /scannow and hit enter. Now it will take some time to complete the scan. It will now display if any file is broken.

If you can’t run an SFC scan or if the SFC scan can’t fix the problem then you need to run a DISM scan instead. To do it:

  • Press the Windows button and type CMD. Now open the CMD with Admin rights.
  • Now enter the DISM /Online /Cleanup-Image /RestoreHealth and press enter to run the command.

The scan will start now and it can take up to 20 minutes or more. After the scan is completed you can now see if there is an issue with the Windows Defender file. 

If you are unable to run an SFC scan or if the DISM scan doesn’t solve the problem then repeat the SFC scan again and again and check if it solves the issues. If not, then check the next method. 

Boot clean your PC

If you have downloaded shady third-party softwares then it will interfere with your Windows files and can cause this problem. But you can resolve this issue by performing a clean boot. To do it:

  • Press Windows Key + R and enter msconfig and hit Enter.
  • Now a System Configuration window will appear. Go to the Services tab and check to Hide all Microsoft services. Now click the Disable all button.
Press Windows Key + R and enter msconfig and hit Enter.
Now a System Configuration window will appear. Go to the Services tab and check to Hide all Microsoft services. Now click the Disable all button.
  • Navigate to the Startup tab and open Task Manager.
  • Now you’ll see a list of startup applications in the Startup tab. Right-click the first entry on the list and choose Disable. Repeat this step for all startup applications.
Now you’ll see a list of startup applications in the Startup tab. Right-click the first entry on the list and choose Disable. Repeat this step for all startup applications.
  • Once you are done with disabling all the startup applications, go back to the System Configuration window and click Apply and OK
  • Now restart your PC.

After restarting the PC check if the problem persists. If not then it means one of the disabled apps was causing the problem. 

Restart the Security Center Service

Some services are essential for working on the Windows Defender and if you don’t have certain services enabled then Windows Defender won’t turn on. 

To start the necessary services do the following:

  • Press Windows key + R  and type services.msc and hit enter. 
  • Inside the services, search for Security Center. Right-click on it and click on Restart.
  • Once you restart the required services, check if the problem with Windows Defender is resolved.

Change your group policy

Sometimes Windows Defender won’t turn on because it’s disabled by your group policy. You can fix this problem, simply by changing the group policy. To do that, just follow these steps:

  • Press Windows Key + R and enter gpedit.msc. Now press Enter.
  • In the left panel navigate to Computer Configuration Administrative Template > Windows Components > Windows Defender Antivirus
  • Now in the right panel, double click on the Turn off Windows Defender Antivirus.
  • Now select Not Configured and click on Apply and OK to save changes.

This should solve the problem and if not then you can try the next fix.

Modify your registry

If Windows Defender won’t turn on, the problem might be in your computer’s registry. However, you can easily modify your registry and fix this issue by doing the following:

  • Press Windows Key + R and enter regedit. Press Enter.
  • When Registry Editor opens, navigate to HKEY_LOCAL_MACHINE > SOFTWARE > Policies Microsoft > Windows Defender in the left panel. 
  • In the right panel, look for DisableAntiSpyware DWORD and double click on it.
  • If the DWORD isn’t available, then click on the Edit tab at the top choose New > DWORD (32-bit) Value from the menu.
  • Set Value data to 0 and click OK to save changes.

After doing that, Windows Defender should be enabled on your PC and it will start working without any problems.

If the above method confuses you then you can use the Command Prompt to do this task. Open Command Prompt with Administrator rights and then: 

  • Copy-paste REG ADD “HKLMSOFTWAREPoliciesMicrosoftWindows Defender” /v DisableAntiSpyware /t REG_DWORD /d 0 /f as it is and hit enter. 

After doing that, the selected DWORD will be instantly changed to 0 and the problem should be resolved.

Check the date or time on your PC

Another issue that is preventing Windows Defender from working properly is the incorrect date and time of your computer. Most of the Windows OS functions work based on the date and time. 

So if the date and time are incorrect it could be abnormal behavior in your Windows OS. To fix this: 

  • Go to Start and type Change date and time and open it.
  • Now you can change the date and time according to your suitable time or set it to automatic. 

Restart your computer and then turn on Windows Defender back on to see if it worked. 

Run Windows Update

Another important feature that could cause the Windows Defender to not run properly is when you fail to update your Windows PC. When it comes to any security software or any software, in general, it needs to have the latest signature updates and other Windows Core Updates to keep your PC secure. 

To update your PC:

  • Press the Windows key and type Windows Update, now click on Open in the right panel. 
  • Now click on update to update your PC. 

Check Internet Zone settings

An incorrect zone setting in Internet Explorer is a minor issue and you can fix it by resetting Internet Explorer to factory settings. But if you are using a Proxy server then Windows Defender will not be able to update.

For this:

  • Open CMD with admin rights.
  • Type the following command and hit enter: Type in the following and hit Enter:
  • Now reboot the system and see if it works.

Check Group Policy setting

Open Group Policy Editor and navigate to the following setting:

Computer Configuration > Administrative Template Windows Components Windows Defender Antivirus.

In the right panel, double-click on Turn off Windows Defender Antivirus.

Next, select the Not Configured option, and then click the Apply and OK button.

Restart the Security Center Service

For the Windows Defender to work properly, you need to enable certain services. If those services aren’t turned on, then the Windows Defender won’t turn on. So, follow the instructions to restart the necessary services: 

  • Click Windows+R keys type services.msc in the box and press Enter.
  • In the Services interface, search for Security Center service and right-click on it to choose the Restart option.
  • Once this service is restarted, you can check if the issue -Windows Defender not starting is solved.

Set Windows Defender Service to Automatic

To set the Windows Defender Service to Automatic:

  • Press Windows+R and type services.msc and hit Enter.
  • Find the following services in the Services window:
    • Windows Defender Antivirus Network Inspection Service
    • Windows Defender Antivirus Service
    • Windows Defender Security Center Service
  • Double-click on each of them and check whether their Startup type is set to Automatic and click Start if the services are not already running.
  • Click Apply and then OK.
  • Reboot your PC to save changes and see if the Windows Defender issue is solved.

Update Windows Defender

To update Windows Defender 

  • Press Windows Key + X then select Command Prompt (Admin).
  • Type the following command into cmd and hit Enter after each one:
    • “%PROGRAMFILES%\Windows Defender\MPCMDRUN.exe” -RemoveDefinitions -All
    • “%PROGRAMFILES%\Windows Defender\MPCMDRUN.exe” -SignatureUpdate
  • Now reboot your PC.


Now I hope you know how to fix Windows Defender when it is not working. If you have any doubts then do comment down below.


Can you download Windows Defender?

Yes, you can download the Windows Defender tool. To download it you need to know whether your computer is using 32-bit or 64-bit? Right-click on My Computer and select Properties. Now you can see whether you are running 32-bit or 64-bit beside the System Type.
32-bit version: Windows 7 / 8 or 8.1 / 10
64-bit version: Windows 7 / 8 or 8.1 / 10

Do I need another antivirus if I have Windows Defender?

Actually no, if you have already installed an antivirus you don’t need to remove it for the Windows Defender to work. You can use them both.

How can I tell if Windows Defender is working?

Open Task Manager and click on the Details tab. Scroll down and look for MsMpEng.exe and the Status column will show if it’s running.
If you don’t find it running then go to Settings – Update & Security and choose Windows Defender in the left panel. At the bottom, you will find “Use Windows Defender“. This will show the last time it ran a scan.

How do I turn Windows Defender on?

Open Control Panel –> then select Administrative Tools –> Edit group policy.
This will open the Local Group Policy Editor in a new window.
Open Computer Configuration –> Administrative Templates –> Windows Components –> Windows Defender Antivirus. The setting Turn off Windows Defender Antivirus is underneath the folders of other settings.
Open Turn off Windows Defender Antivirus and make sure it’s set to Disabled or Not configured.

Thank You!!!

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