Quick Fix: Windows Defender not Turning on (7 ways)

What Is Windows Defender?

Windows Defender is a built-in antivirus in Windows 10 and it is also known as Windows Defender Security Center. It provides real-time protection to your computer against various network threats such as spyware, malware, hackers and viruses. If this software finds any potential threats, it will block them immediately. 

But many Windows 10 users report that Windows Defender won’t start in Windows 10. You can read on to learn the reasons and how to turn on Windows Defender in Windows 10.

Why Windows Defender not Turning on?

Anti-virus software is critical in keeping your computer security. Whether you are connected to a public WIFI or your private network, you are at risk for a variety of virus attacks. Some malware can even spread offline.

So, if Windows Defender missing or not turning on, it can be very dangerous for your computer. There are many reasons for Windows Defender not turning on, the common ones are as follows.

 You have installed another third-party security software that interferes with Windows Defender.

 Errors in Windows Defender related service.

 You are using an older version of Windows 10.

 There is a system configuration error on your device.

 Windows Defender is disabled or turned off in Group Policy.

 Registry Editor prevents Windows Defender from opening.

 There is a malware infection on your computer.

How to Fix Windows Defender not Turning on

Next, this article will introduce you different solutions based on the reasons mentioned above. And you can try these ways to fix Windows Defender not turning on. Please read on for more details.

Fix 1. Uninstall Another Third-party Security Software

If you have installed another third-party antivirus on your computer, it may interfere with Windows Defender and cause the Windows Defender not turning on. Therefore, you can first uninstall the third-party security software. Then restart your computer to see if you can open Windows Defender properly.

Fix 2. Restart the Security Center Service

You need to enable certain services for Windows Defender to work properly. You can follow the steps below to restart the Security Center service. Once the services are restarted, you can open Windows Defender again to see if it works normally.

Step 1. Press Win + R together to open the Run window, then type services.msc in the box and press Enter.

Step 2. On the Services page, search for Security Center service and right-click on it to select Restart.

Fix 3. Check System Files via System File Checker

If there is a problem with the system files, then it can also cause the Windows Defender not turning on. You can use Windows system file checker SFC to check the system files. Please follow the steps below.

Step 1. Press Win + S and type cmd, then click Run as administrator to start Command Prompt as administrator.

Step 2. Type the following command and hit Enter, then wait patiently for the scan to complete.

sfc /scannow

Step 3. When the process has been done, exit the CMD window to check whether Windows Defender not turning on error is fixed.

Run DISM

If you can’t run an SFC scan or if SFC can’t fix the problem, you can try DISM scan to help you. You can follow the steps below.

Step 1. Start Command Prompt as administrator, as shown in the previous step.

Step 2. Type the following command and hit Enter. And the process also will take some time, please wait patiently and don't interrupt it.

DISM /Online /Cleanup-Image /RestoreHealth

Fix 4. Install the Latest Update of Windows 10

Some users have reported that they just updated to the latest Windows 10 and they can turn on the Windows Defender. If you are using an older version of Windows 10, you can try to install the latest update of Windows 10 and then check if Windows Defender opens properly. By the way, Before updating your system, it is recommended that you make a system backup to protect your data.

Fix 5. Change the Group Policy Editor

Windows Defender is disabled or turned off in Group Policy can also cause Windows Defender not turning on. You can follow the steps below to fix it.

Step 1. Enter gpedit.msc in the Run window and press Enter to open Group Policy.

Step 2. Then navigate to the following path.

Computer Configuration/ Administrative Template/ Windows Components/ Microsoft Defender Antivirus

Step 3. In the right pane, double-click on Turn off Windows Defender Antivirus.

Step 4. When you see the pop-up window, choose Not Configured, click Apply and then click OK.

Tip:

The Group Policy Editor wasn't included in Windows 10 Home edition. If you want to use it, you need to first download and install Group Policy Editor.

Fix 6. Modify the Windows Registry Editor

If Windows Defender is not opening because of the Registry Editor, then you can follow the steps below to modify the Registry Editor.

Step 1. Type regedit in the Run window to open the Registry Editor.

Step 2. Then navigate to the following path.

HKEY_LOCAL_MACHINE/SOFTWARE/Policies/Microsoft/Windows Defender 

Step 3. In the right pane, find DisableAntiSpyware and double click it. If this key is not listed, please right-click the blank, choose New and DWORD (32-bit) Value to create it.

Step 4. Set the Value data to 0 and click OK to save the changes.

Fix 7. Clean Boot Your Computer

If there are a lot of third-party applications running in the background, then this may interfere with Windows and cause Windows Defender not turning on. You can fix it by performing a clean boot.

Step 1. Type msconfig in the Run window and press Enter.

Step 2. In the System Configuration page, click the General tab, choose Selective startup and uncheck Load startup items then click OK.

Step 3. Click the Services tab and tick Hide all Microsoft services box. Then click Disable all button and click OK.

Then, you can restart your computer to check if the Windows Defender can turn on normally.

Another Way to Protect Windows System from Virus Attack (Double Protection)

After you fix Windows Defender, it will turn on normally to protect your computer. But sometimes it may go wrong again. Therefore, you cannot only rely on Windows Defender to protect your computer. It's recommended that you make a system backup and put it on an external disk to secure your system. In this way, you will have double insurance.

After that, even if Windows Defender fails to open to protect your computer or there is any other problem with your computer, you can use this system backup to restore and then let the computer work normally without data loss.

The free backup and restore software AOMEI Backupper Standard can help you achieve this goal easily with its System Backup feature. And it also provides a variety of backup solutions to meet your different needs, such as Disk Backup, Partition Backup and File Backup. It also has the following advantages.

Schedule backup: It allows you to backup your system with fixed intervals such as Daily, Weekly or Monthly.

Incremental backup: It’s very helpful for scheduled backup, because this backup method will only backup the changed parts to save the disk space.

Multiple destination locations: You can backup your system to different locations, such as local disk, external disk, HDD, SSD, USB drive, etc.

Powerful compatibility of OS: It supports various operating systems, such as Windows 11/10/8/7/XP/Vista, etc.

Then you can follow the graphic tutorial below to backup your system to prevent virus attacks or other dangers.

Step 1. Download AOMEI Backupper Standard, install and launch it. Then click Backup > System Backup.

Step 2. It will select the boot-related partitions automatically. And you just need to select an external disk as the destination location to store your system backup.

Step 3. Click Start Backup to backup your system.

Notes:

• Options: It allows you to write comments to distinguish the different backups, choose the compression level or set email notifications for your system backup.
• Schedule: You can set the frequency to run the scheduled backup automatically, such as Daily, Weekly, Monthly, Event Trigger and USB plug in. The professional version supports the last two features.
• Scheme: It will delete older backups to save your disk space as well as select different backup methods for your system backup. And you can upgrade to AOMEI Backupper Professional or higher versions to enjoy it.

Summary

This article shows you how to fix Windows Defender not turning on, and you can use the 7 methods mentioned in the article to help you. But sometimes the error may occur again, so you cannot just rely on it to protect your computer.

You can use the free backup software AOMEI Backupper Standard to make a system backup to an external disk. This is equivalent to having double insurance. Even if Windows Defender fails to open, this system backup can still help you protect your data. You can use this system backup to restore it and then use your computer normally.

Besides, it is also an excellent cloning software, it offers various cloning functions including System Clone, Disk Clone and Partition Clone. Its Disk Clone feature even allows you to clone a large disk to a small one. After cloning, you can boot your computer directly from the cloned disk. You can download this software to explore more useful features.