How to Optimize Microsoft Defender CPU Usage in Windows 11

What is Microsoft Defender Antivirus?

Microsoft Defender Antivirus provides built-in threat protection for Windows 11 by scanning files in real time.

Active sweeps occasionally spike hardware utilization past 50%. Capping that threshold prevents system slowdowns during intensive tasks, though tighter constraints mean scans take longer to finish.

Why Would You Want to Change This?

Limiting resource consumption keeps the desktop responsive while security checks run in the background. Multitasking remains smooth even during a deep system inspection.

How to Change CPU Usage During Scans

Three distinct methods allow administrators to adjust how much processor power Defender uses during analysis:

1Using PowerShell (Easy for Everyone)

You can lower Microsoft Defender CPU usage quickly by running a simple command in PowerShell. This lets you set a strict limit on how much processor power antivirus scans can use in the background, keeping your computer fast and responsive while security checks run.

Or: Press Windows key + S, type PowerShell, right-click it, and select Run as administrator. [ADMIN REQUIRED]

Step 2: Check your current CPU limit

Copy and paste this command and press Enter:

Get-MpPreference | select ScanAvgCPULoadFactor

Console output will display the active restriction value, which typically defaults to 50.

Step 3: Set a new CPU limit

Run the command below, swapping <percentage> for an integer between 0 and 100:

Set-MpPreference -ScanAvgCPULoadFactor <percentage>

Example: Restricting the antivirus engine to a maximum 30 percent threshold requires executing:

Set-MpPreference -ScanAvgCPULoadFactor 30

Step 4: Restart your computer

Reboot the machine to enforce the updated parameters.

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

You can reduce Microsoft Defender CPU usage on Windows 11 Pro and Enterprise by changing settings in the Local Group Policy Editor. This built-in tool lets you place a hard cap on processor power for background scans so your PC stays fast during security checks.

Step 1: Open Local Group Policy Editor

Press Windows key + R, type gpedit.msc, and press Enter. [ADMIN REQUIRED]

Step 2: Navigate to the Scan folder

Go to this location:

Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus → Scan

Step 3: Find and edit the CPU setting

Click the Scan directory in the left sidebar, then double-click "Specify the maximum percentage of CPU utilization during a scan" on the right panel.

Step 4: Enable and set your percentage

Choose Enabled, then type any integer from 0 to 100 into the percentage field.

Step 5: Apply changes

Click Apply and OK.

Step 6: Restart your computer

Reboot the operating system to apply the configuration.

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

You can limit Microsoft Defender CPU usage using Registry Editor if you use Windows 11 Home and do not have the Group Policy Editor. Editing the system registry lets you manually set a processor limit for antivirus scans to keep your computer running smoothly.

Step 1: Open Registry Editor

Press Windows key + R, type regedit, and press Enter. [ADMIN REQUIRED]

Step 2: Navigate to the Defender Scan folder

Go to this location:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Scan

Step 3: Create the Scan folder if it doesn't exist

Locate the Windows Security registry key, right-click it, select New, then Key, and name the resulting directory Scan. This establishes a dedicated container for scanning preferences.

Step 4: Create a new value

Select the Scan directory, right-click any empty space in the right pane, hover over New, and pick DWORD (32-bit) Value. Name this newly generated entry AvgCPULoadFactor.

Step 5: Set the CPU percentage

Double-click the new entry, select 'Decimal' for the base, and type a number from 0 to 100. Entering 25, for instance, restricts background scans to a quarter of total processing power, overriding the default value of 50.

Step 6: Save and close

Click OK and close the Registry Editor window.

Step 7: Restart your computer

Reboot the computer to validate the configuration.

Important Note: Always back up the registry prior to making modifications. Incorrect entries can destabilize the operating system.

What Happens When You Lower CPU Usage?

System responsiveness improves noticeably during active scans, letting intensive applications run smoothly. The sole trade-off involves longer completion times for full system checks.

Summary

Managing Microsoft Defender CPU usage prevents background antivirus scans from slowing down your computer. Choosing any of the methods above gives you direct control over processor limits, keeping your system fast and responsive while staying fully protected.

Selecting any of these administrative pathways gives fine-grained control over system behavior. Pick the environment that matches your administrative preference.

Throttling processor utilization maintains overall desktop speed during security sweeps while marginally extending scan durations.

Rebooting the hardware following any configuration change guarantees the modified parameters initialize correctly.

Consult official documentation via Configure scanning options for Microsoft Defender for deeper technical specifications.

Readers are welcome to share questions or alternative performance tweaks in the comment section below. Community contributions help fellow users overcome hardware bottlenecks on Windows 11.