Forum Discussion
Windows 11: Antivirus causes high CPU usage
My antivirus software is causing persistently high CPU usage, often peaking at 100% and slowing down my entire system even during idle periods. This performance hit occurs during both scheduled scans and real-time protection, and I need advice on adjusting settings or finding a lighter security solution.
3 Replies
First identify which protection component is actually consuming the CPU; do not exclude Windows or system folders from real-time scanning.
1. Open Task Manager, sort by CPU, and note the exact process name during an idle spike and during a scheduled scan.
2. If Microsoft Defender is the active antivirus, open Windows Security > Virus & threat protection > Manage settings and confirm that no second real-time antivirus is still registered under Security providers.
3. Schedule full scans outside working hours and keep real-time protection enabled.
4. To find files or processes that repeatedly trigger Defender, open PowerShell as administrator and run New-MpPerformanceRecording -RecordTo C:Defender.etl, reproduce the high CPU period for a few minutes, stop the recording, then run Get-MpPerformanceReport -Path C:Defender.etl -TopFiles 20 -TopProcesses 20.
Use the report to correct a looping build folder, archive or process only when you understand why it is repeatedly scanned. Add a narrow exclusion only for a trusted, high-churn data folder, never for C:Windows, the whole system drive or user profiles.
In your antivirus software settings, exclude the system folder from real-time protection scans, or switch to Windows Defender, which uses fewer system resources.
Having two antivirus programs running simultaneously often leads to performance issues and conflicts. Ensure you only have one active security suite installed.
