Blog

Windows Defender is an essential security tool built into Windows 11 to protect your computer from viruses and malware. However, sometimes it can use a lot of your CPU resources, which slows down your system. This guide will help you fix Windows Defender high CPU usage step-by-step.

High CPU usage by Windows Defender can happen due to various reasons, such as real-time scanning, scheduled scans, or conflicts with other software. Understanding these causes will help you address the issue effectively.

We will start with simple checks and progress to more advanced solutions. Each step includes a clear explanation so you know why it is important.

By following this guide, you should be able to reduce Windows Defender’s CPU usage and improve your Windows 11 computer’s performance.

Quick Note: Before You Begin

Before troubleshooting, it’s good to check a few things:

• Make sure Windows 11 is fully updated. Sometimes updates fix performance bugs.
• Confirm that no other antivirus programs are running alongside Windows Defender, as this can cause conflicts.
• Save your work before starting, as some steps may require restarting your system.

Step 1: Pause Windows Defender Real-Time Protection Temporarily

Windows Defender’s real-time protection constantly scans files as you use your PC. This can cause high CPU usage especially if many files are being scanned.

To check if this is the issue, try temporarily disabling real-time protection:

1. Click the Start button and select Settings.
2. Go to Privacy & security > Windows Security.
3. Click Virus & threat protection.
4. Under Virus & threat protection settings, select Manage settings.
5. Turn off the toggle for Real-time protection.

Use your computer for a few minutes and check if CPU usage improves. Remember to turn real-time protection back on afterward to keep your PC safe.

Step 2: Run a Quick Scan and Check for Malware

Sometimes malware or viruses can cause Windows Defender to work harder than usual. Running a quick scan can help detect and remove such threats.

Here’s how to do a quick scan:

1. Open Windows Security via the Start menu.
2. Click on Virus & threat protection.
3. Press the Quick scan button.
4. Wait for the scan to complete and follow any instructions if threats are found.

After the scan, monitor CPU usage again to see if the problem persists.

Step 3: Check and Exclude Large or Frequent Files/Folders from Scans

Windows Defender may use high CPU if it repeatedly scans large files or folders that change often, like downloads or certain app folders.

You can exclude these files or folders to reduce CPU load:

1. Go to Windows Security > Virus & threat protection > Manage settings.
2. Scroll down to Exclusions and click Add or remove exclusions.
3. Click Add an exclusion and select Folder or File.
4. Choose folders or files that you trust and that are large or frequently updated.

Be cautious with exclusions to avoid leaving your PC vulnerable.

Step 4: Adjust Windows Defender Scheduled Scan Timing

Windows Defender runs scheduled scans automatically, which can cause CPU spikes if they run during your active hours.

You can change the scan schedule using the Task Scheduler:

1. Press Windows + S, type Task Scheduler, and open it.
2. Expand Task Scheduler Library > Microsoft > Windows > Windows Defender.
3. Right-click Windows Defender Scheduled Scan and choose Properties.
4. Go to the Triggers tab and click Edit.
5. Change the time to a period when you are less likely to use your PC, like late night.
6. Click OK and close Task Scheduler.

This helps avoid scan-related CPU spikes during busy times.

Step 5: Disable Windows Defender’s Cloud-Delivered Protection (Optional)

Cloud-delivered protection improves security by sending data to Microsoft, but it can sometimes increase CPU usage.

If you want to try disabling it:

1. Open Windows Security.
2. Go to Virus & threat protection > Manage settings.
3. Turn off Cloud-delivered protection.

Note that disabling this reduces threat detection capabilities, so only do this if CPU usage remains very high.

Step 6: Check for Conflicting Software

Running multiple antivirus or security programs simultaneously can cause conflicts and high CPU usage.

To check:

• Press Ctrl + Shift + Esc to open Task Manager.
• Look for other antivirus programs running in the background.
• If found, consider disabling or uninstalling them, as Windows Defender works best when it is the sole antivirus tool.

This reduces resource conflicts and improves performance.

Step 7: Scan and Repair System Files Using SFC

Corrupted system files can cause Windows Defender to malfunction. Running the System File Checker (SFC) tool can repair these files.

Here’s how:

1. Press Windows + S, type cmd, right-click Command Prompt, and choose Run as administrator.
2. Type the following command and press Enter:

sfc /scannow

The scan will take some time. If any corrupted files are found, the tool will attempt to fix them automatically.

Restart your computer when the scan is complete and check CPU usage again.

FAQs

Why is Windows Defender using so much CPU?

Windows Defender uses CPU mostly when scanning files, running updates, or dealing with potential threats. High CPU usage can also result from conflicts or corrupted system files.

Is it safe to disable Windows Defender real-time protection?

Disabling real-time protection temporarily can help in troubleshooting, but it leaves your PC vulnerable if left off for long periods. Always turn it back on once you finish testing.

Can I add exclusions without risking security?

Adding exclusions can improve performance but increases risk if you exclude unsafe files. Only exclude files or folders you trust completely.

Should I uninstall other antivirus programs if I use Windows Defender?

Yes, running multiple antivirus tools can cause conflicts. It’s best to use only one antivirus program at a time.

What if Windows Defender keeps using high CPU even after trying these steps?

There may be deeper system issues or malware infections. Consider professional support or additional malware removal tools.

When Nothing Works

If you have tried all the steps above and Windows Defender still uses high CPU, you can try the following:

• Reset Windows Security: You can reset the app by going to Settings > Apps > Installed apps, finding Windows Security, and selecting Advanced options > Reset.
• Use Microsoft’s Support and Recovery Assistant: Visit the official Microsoft website for tools to diagnose and fix Windows Security problems.
• Consider a Clean Boot: This starts Windows with minimal drivers and startup programs to identify conflicts.
• Contact Microsoft Support: If the issue persists, official support can provide personalized assistance.

Conclusion

High CPU usage by Windows Defender on Windows 11 can be frustrating, but most issues can be fixed with simple steps like pausing real-time protection temporarily, adjusting scan settings, or excluding certain files.

Always keep your system updated and run regular scans to maintain security. If problems continue, advanced troubleshooting like system file repair or resetting Windows Security may be necessary.

Following this guide will help you balance protection and performance so your Windows 11 PC runs smoothly while staying safe.