CPU Usage Stuck at 100%
Intermediate
Performance & Slow PC
Applies to: Windows 10, Windows 11
Performance & Slow PC
Applies to: Windows 10, Windows 11
The fans are loud and everything lags, even with nothing obviously demanding open.
Before you start: save any open work and note down what you were doing when the problem started — that context helps if you need to search further or ask for help.
- Open Task Manager and sort by CPU to identify exactly what's using it — don't guess.
- If it's "System" or a Windows process, search Task Manager > Details for the specific process name and look it up before ending it, since some are essential.
- Check for pending Windows Updates installing in the background — this is a very common, temporary cause of high CPU.
- Run a malware scan with Windows Security (Settings > Privacy & security > Windows Security > Virus & threat protection) — cryptomining malware is a real cause of sustained 100% usage.
- If a specific app is consistently the cause, check for an updated version — a buggy release is often the real problem, not your hardware.
Still not fixed? Send us the details and we'll help you dig further, or browse related guides in Performance & Slow PC.
Frequently Asked Questions
Is it normal for CPU usage to spike briefly?
Yes — brief spikes when opening apps or during background tasks are completely normal. It's only worth troubleshooting if usage stays pinned near 100% for extended periods while the PC is otherwise idle.
Could a browser really be causing high CPU usage?
Yes, easily — a single misbehaving tab, a heavy extension, or too many open tabs are common, often-overlooked causes of sustained high CPU usage, especially with modern web apps.
Related guides
My PC Has Gotten Noticeably Slower
General sluggishness with no single obvious cause.
Disk Usage Stuck at 100%
Task Manager shows the disk pegged even when you're not doing anything heavy.
PC Randomly Freezes or Stutters
Everything locks up for a few seconds to a minute, then resumes on its own.