To turn off Windows Defender (now called Microsoft Defender Antivirus), there are two main ways depending on whether you want to disable it temporarily or permanently.

Temporarily Turn Off Windows Defender

1. Click the Start button.
2. Type Windows Security and open it.
3. Go to Virus & threat protection.
4. Click on Manage settings under Virus & threat protection settings.
5. Toggle Real-time protection to Off.
   This temporarily disables Defender until the next system reboot, when it will turn back on automatically.

Permanently Disable Windows Defender

There are three main methods to permanently turn it off:

1. Using Group Policy Editor (Windows Pro/Enterprise)
   • Press Win + R , type gpedit.msc , and press Enter.
   • Navigate to: Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus.
   • Double-click Turn off Microsoft Defender Antivirus.
   • Select Enabled , click Apply , then OK.
   • Restart your computer.

2. Using Registry Editor (Windows Home/Pro)
   • Press Win + R , type regedit , and press Enter.
   • Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender.
   • Right-click, choose New > DWORD (32-bit) Value, and name it DisableAntiSpyware.
   • Double-click on it and set the value data to 1.
   • Restart your computer.

3. Using PowerShell (Advanced Users)
   • Open PowerShell as Administrator.
   • Run the command: Set-MpPreference -DisableRealtimeMonitoring $true.
     This disables real-time monitoring but may need to be combined with Group Policy or Registry changes for permanent effect.

Note: Disabling Windows Defender reduces your protection against malware and cyber threats. Make sure to have another antivirus solution in place if you choose to disable Microsoft Defender permanently. This covers both temporary and permanent ways to turn off Windows Defender in Windows 10 and Windows 11 systems.