Windows Defender won't open? Here's how to fix it! (Windows 11)

Last edited: 23/4/2024

[PLEASE NOTE BEFORE READING]

This fix is more than 2 years old. There is a high likelihood that it may not work on your system.

BEFORE YOU COMMENT, "It doesn't work" or "Not working," PLEASE REMEMBER! There are actual users looking in the replies for other solutions as well. If it does not work for you, please also include the errors that you encountered and which step you got stuck on. This way also gives me a chance to possibly help you.

If you can't or do not want to include more information on not being able to proceed with this fix, simply move on and try other fixes.

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Remember: Make sure you are using an administrator account, are the owner of the device, or have permission from the administrator to proceed with these steps.

Windows 11 is a brand new OS. Windows Security may not be opening, as many users have said. The following steps may fix this issue for you:

Step 1: In search, type "PowerShell"

Step 2 As PowerShell appears, press "Run as Administrator" Click "Yes" on the following prompt.

Step 3: Enter the following commands separately in order shown.

1. Set-ExecutionPolicy Unrestricted

(If it prompts you with (Y/N) which is "Yes or No", type Y. If not, proceed to the next step)

2. Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register “$($_.InstallLocation)\AppXManifest.xml”}

Added by mod (ty): Revert execution policy.

3. Set-ExecutionPolicy Restricted

Try opening Windows Security after. It should now work. Feel free to post any other solutions and questions.

EDIT:

This second option will work even if you are not an administrator:

https://techcommunity.microsoft.com/t5/windows-insider-program/issue-with-windows-defender-on-windows-11/m-p/3261866/highlight/true#M15320

Link suggested by hiThereSomeUserHere.

Suggested by Amirali Hendi:

Download the Windows Security App from the Microsoft website. The link: https://www.microsoft.com/en-us/microsoft-365/microsoft-defender-for-individuals

launch it and log in to your Microsoft account. Then close it. Now you can launch the Windows Security app!

(I am not a Microsoft official, so I cannot promise that this will not harm your computer. Make sure you have permission from the administrator before doing this.)