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High CPU usage in Windows is one of the most common reasons a PC feels slow — fans spin up, apps stutter and everything takes forever to load. The good news is that most causes are software, and you can usually fix them in a few minutes with the built-in tools Windows already has.
Step 1: find out what is using the CPU
Press Ctrl + Shift + Esc to open Task Manager, then click the CPU column to sort by usage. The process at the top is the one eating your CPU. It might be a browser with too many tabs, a game update, Windows Update running in the background, or an antivirus scan. If the top process is something you recognise, close it and see if the usage drops. For more on how to read CPU numbers, see our CPU benchmarks explained guide and our how to benchmark your CPU guide.
Step 2: end the problem process
If one app is stuck at 50% or more, select it in Task Manager and click End task. If it comes back right away, restart your PC — a simple restart fixes more high CPU usage problems than anything else. If the process is one you do not recognise, run a full malware scan, because malware is a common cause of high CPU usage. Check your temperatures too: a hot CPU throttles and looks slow, and our why is my CPU overheating guide covers the fixes.
Step 3: update Windows and your drivers
Out-of-date Windows or bad drivers can push CPU usage up for no clear reason. Open Settings, go to Windows Update and install any pending updates, then restart. Next, update your chipset and graphics drivers from the manufacturer’s site — do not rely on old drivers that came on a disc. A clean driver update often fixes usage spikes that appear after a Windows update. Our AM5 BIOS update guide also covers BIOS updates, which can help on AMD boards.
Step 4: turn off startup programs
Too many apps starting with Windows will keep your CPU busy long after you log in. In Task Manager, open the Startup apps tab and disable anything you do not need at login — chat apps, cloud sync tools, game launchers and updaters. You can still open them when you need them; they just will not run in the background. This is one of the easiest wins for an older PC, and it pairs well with our best budget CPU for office work advice if your chip is simply too weak for the job.
Step 5: check the background services
Some Windows services use a lot of CPU for a while and then settle down — Windows Update, search indexing and the Microsoft Store are the usual ones. Give them a few minutes after a fresh install or a big update. If a service stays high for hours, open Services, find it and restart it, or disable it if you do not use it. Our how to monitor CPU temperature guide shows you how to watch both usage and temperature while you test.
When it is a hardware problem
If your CPU stays at 100% even with nothing open, the problem may be the chip itself. Check the cooler: a loose cooler or dried-out thermal paste lets the CPU overheat and throttle, which keeps usage high. Our how to apply thermal paste correctly guide and our CPU cooling basics guide can help. If the chip is old and genuinely too weak for today’s apps, see our best budget CPU under $100 guide for a cheap replacement.
The bottom line
High CPU usage in Windows is almost always fixable: find the process, end it, update your drivers and trim your startup apps. If the usage stays high after that, check the cooler and the temperature. For more help, browse our troubleshooting tips and our CPU benchmarks guides to test your chip.
