Windows Defender not working [FULL FIX]

Ivan Jenic
by Ivan Jenic
Troubleshooting Expert
Passionate about all elements related to Windows and combined with his innate curiosity, Ivan has delved deep into understanding this operating system, with a specialization in drivers and driver troubleshooting. When he's not tackling... Read more
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  • There are instances when a computer is not protected because Windows Defender won't turn on Windows.
  • If Windows Defender real-time protection won't turn on Windows 10, then you should check its settings.
  • Sometimes, the date and time settings are the reason why Windows Defender won't turn on.
  • Using dedicated software solves the failure of the Windows Defender antivirus to turn on in Windows 10.
windows defender won't turn on
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Often we hear people complaining that they cannot turn on Windows Defender in Windows 10, so today we’ve decided to share with you a few tips on how to fix this issue.

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Windows Defender won’t start

Here are some examples of how this issue may manifest itself:

  • Can’t turn on Windows Defender Windows 10 Group Policy
  • Can’t turn off Windows Defender Windows 10
    • If  you want to switch to another antivirus program, this problem might prevent you from turning off Windows Defender.
  • Windows Defender real-time protection handled by another av program
    • Windows Defender and another antivirus program don’t go along (see below).

There are a few possible scenarios for this problem, and we’ll cover most of them in this article.


What to do if Windows Defender is not working in Windows 10


  1. Enable real time protection
  2. Change date and time
  3. Use professional software for protection
  4. Update Windows
  5. Change Proxy Server
  6. Disable third-party antivirus
  7. Run the SFC scan
  8. Run DISM
  9. Reset the Security Center service

1. Enable real-time protection

  1. Press the Windows key + Q key on the keyboard to bring up the charms search.
  2. Type Windows Defender in the search box and then press Enter.
  3. Head over to the Settings and check Turn on real time protection.

Windows Defender is designed to turn itself off if it detects any other third-party antivirus software. Windows is designed to detect any installed antivirus software, and certain issues can occur if you have two or more antivirus software installed.

These issues include conflicts between antivirus software that can manifest as frequent freezing, crashing to applications, etc.

Since this is a common problem, in order to avoid any conflicts, Windows Defender will turn itself off if Windows detects any other security program.

In addition, if this security software has a Firewall, Windows Firewall will also turn itself off.

This means that if you want Windows Defender to work, you’ll have to choose between it and the third-party antivirus software.

Often users are not aware of whether security software is installed or not because when you buy a new laptop in most cases it comes with a trial version of antivirus software such as Norton, McAfee etc.

When you install applications like Flash or Java it might prompt you to uninstall the free security scanner, and that can cause some problems.

Therefore it’s best to search your PC if you’re not sure whether security software is installed or not. Once you remove it, you might need to manually turn it back on using these steps:


2. Change date and time

Another cause for Windows Defender to not work properly is incorrect time and date on Windows 10.

In order to fix this, you need to check your time and date and set it to the correct value before trying to turn Windows Defender back on.

We know that this might sound strange, but most of the Windows system functions are dependent on time and date, therefore an incorrect date or time could trigger abnormal behavior in your Windows OS.


3. Use professional software for protection

Windows Defender is a useful feature for your operating system, but if it doesn’t function properly, you can try profesionnal software. This program is constantly improved through updates by its developer so that it will detect and repair the latest malware that will appear.

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4. Update Windows

  1. Go to Start, select Settings, and choose Update & Security.
  2. Navigate to Windows Update, and then select Check for updates.Windows updates

Make sure that you keep your Windows up to date using Windows Update since this can cause some problems with Windows Defender. When it comes to any security software, make sure that you update it frequently.

We suggest that you perform a full Windows Update, then open Windows Defender and run an update from there as well.

If you can’t open the Setting app, we have a special article for how to solve the issue.


5. Change Proxy Server

  1. Press Windows key + X and select Command Prompt (Admin).cmd prompt
  2. Type in one of the following:  NETSH WINHTTP SET PROXY 1.1.1.1:8080 or NETSH WINHTTP SET PROXY MYPROXY.NET:8080
  3. Reboot the system and see if it works.

These three are most common scenarios that can cause problems with Windows Defender, but there are some other not so common scenarios that can cause problems as well.

For example, incorrect Zone settings in Internet Explorer can cause problems, but you can easily fix this by resetting Internet Explorer to factory settings.

Bear in mind that if you are using a Proxy server, Windows Defender will not be able to update. If that’s the case, you’ll need to make some minor tweaks to your Proxy server.

If you’re having trouble accessing Command Prompt as an admin, then you can read one of our guides.


6. Disable third-party antivirus

Windows Defender doesn’t get along with third-party antivirus programs. Just like any two antivirus programs don’t work well with each other.

So, if you want Windows Defender to be your primary security option, make sure to disable any third-party antivirus programs you have installed on your computer.


7. Run the SFC scan

  1. Go to Search, type cmd, and open Command Prompt as Administrator.Command Prompt
  2. Enter the following line and press Enter:sfc/scannow
  3. Wait for the process to finish.
  4. Restart your computer.

This simple solution shows how to run the SFC scan in Windows 10.


8. Run DISM

  1. Go to Search, type cmd, and open Command Prompt as Administrator.Windows Defender not working
  2. Enter the following command on the command line:
    • DISM.exe /Online /Cleanup-image /Restorehealth
  3. In case the DISM can’t obtain files online, try using your installation USB or DVD. Insert media and type following command:
    • DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:C:RepairSourceWindows /LimitAccess
  4. Make sure to replace the following path of your DVD or USB: C:/Repair/Source/Windows

9. Reset the Security Center service

  1. Go to Search, type services.msc, and open Services.
  2. Find the Security Center service.services.msc
  3. Right-click the Security Center service, and go to Reset.
  4. Restart your computer.

And finally, if none of the solutions from above worked, we’ll try resetting the Security Center service. Hopefully, Windows Defender will start working after that.


That’s about it, we hope at least one of these solutions helped you resolve your problems with Windows Defender. If you have any comments, questions or suggestions, just let us know in the comments down below.

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Frequently Asked Questions

  • One of the reasons might be that you already have a third-party antivirus up and running. A more serious reason would be actual malware that prevents other antivirus programs to start. Use a good anti-malware in this case.

  • Windows Defender runs automatically in the background scanning downloaded files, system files, and so on. It is also scheduled to perform quick system scans but doesn’t really show anything unless it detects something that needs attention.

  • Independent tests for performance and protection have shown Windows Defender performing quite well and seeing an improvement over the years. So for general use, it’s a good choice. For specific needs see our top antivirus with remote management.