If you use Windows 11, Microsoft Defender Antivirus helps protect your computer by scanning for viruses and malware. But sometimes, these scans can use a lot of your computer’s power (CPU), which might slow down other things you’re doing.

Good news! You can control how much CPU Microsoft Defender uses during scans. This guide will show you easy ways to change those settings so your computer runs smoothly.

What is Microsoft Defender Antivirus?

Microsoft Defender Antivirus is built into Windows 11. It regularly scans your computer to keep it safe from harmful software.

By default, Defender uses about 50% of your CPU during scans. On slower computers, this might make things feel sluggish. You can change this number to use less CPU, but keep in mind that lowering it too much might make scans take longer.

How to Change CPU Usage During Scans

You can adjust the CPU usage for scans by using one of these simple methods:

1. Using PowerShell (Easy for Everyone)

PowerShell is a tool in Windows that lets you type commands to change settings.

1. Open PowerShell as Administrator:
   
   Click here to learn how to open PowerShell.
   
   Or: Press Windows key + S, type PowerShell, right-click it, and select Run as administrator.
   
2. Check current CPU limit:
   
   Copy and paste this command and press Enter:
   

   Get-MpPreference | select ScanAvgCPULoadFactor

   
   

   You will see a number showing the current CPU limit (usually 50).
   

3. Set a new CPU limit:
   
   Use this command, replacing <percentage> with a number between 0 and 100:
   

   Set-MpPreference -ScanAvgCPULoadFactor <percentage>

   
   

   Example: To limit Defender to use only 30% CPU, run:

   
   

   Set-MpPreference -ScanAvgCPULoadFactor 30

   
   
4. Restart your computer to apply the new setting.
   

2. Using Local Group Policy Editor (For Windows 11 Pro or Enterprise)

This tool lets you change settings in Windows with a simple interface.

1. Open the Local Group Policy Editor by pressing Windows key + R, typing gpedit.msc, and pressing Enter.
   
2. Navigate to this folder:
   
   Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus → Scan
   
3. Select the Scan folder on the left, then double-click “Specify the maximum percentage of CPU utilization during a scan” on the right.
   
4. Choose Enabled, then enter the CPU percentage you want (0 to 100).
   
5. Click Apply and OK.
   
6. Restart your computer to make the changes take effect.
   

3. Using Windows Registry Editor (If Group Policy Editor is not available)

Be careful with this one! The Registry stores important Windows settings.

1. Open the Registry Editor by pressing Windows key + R, typing regedit, and pressing Enter.
   
2. Go to this folder:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows DefenderScan
   
3. If you don’t see the Scan folder, right-click on Windows Defender, choose New → Key, and name it Scan.
   
4. Click on the Scan folder. On the right side, right-click and choose New → DWORD (32-bit) Value. Name it AvgCPULoadFactor.
   
5. Double-click AvgCPULoadFactor, set the Base to Decimal, and enter a number between 0 and 100 for CPU usage.
   
   (Default is 50)
   
6. Click OK and close the Registry Editor.
7. Restart your computer to apply changes.

Summary

• Microsoft Defender Antivirus scans your PC to keep it safe but can use a lot of CPU during scans.
• You can change how much CPU it uses by using PowerShell, Local Group Policy Editor, or Registry Editor.
• Lowering CPU usage helps your PC run smoother during scans but might make scans take longer.
• After changing settings, always restart your PC for changes to work.

For more official info, see Microsoft’s guide: Configure scanning options for Microsoft Defender.

If you have questions or tips, feel free to share them in the comments below!