kernel_task using high CPU on your Mac: what it means

kernel_task looks like the villain in Activity Monitor. Usually it's the bouncer.

By Andrew Wilson · Updated 2026-11-02

Short answerkernel_task is the core of macOS. Apple says that when the CPU gets too hot, kernel_task takes up CPU time on purpose so other apps can't use it, which lowers heat. So high kernel_task CPU usually means the Mac is already hot from something else: a heavy app, a warm room, blocked airflow, or charging while busy. Fix the heat source and kernel_task goes back down. Never try to quit it.

WhoIsCooking panel showing the Mac's chip temperature and the apps heating it, busiest first — WhoIsCooking shows the chip temperature and which apps are heating the Mac, busiest first, with a one-click Cool down.

What kernel_task is

kernel_task is not an app. It is how Activity Monitor shows the macOS kernel: memory management, drivers, networking, and temperature control all count towards it.

Why it uses so much CPU when the Mac is hot

When the temperature rises too far, macOS needs other processes to do less work. One way it does that is by having kernel_task claim CPU time, which leaves less for the heavy apps. Apple documents this in its support article If kernel_task is using a large percentage of your Mac CPU. The CPU number looks huge, but much of that time is not real work; it's macOS slowing things down to cool the chip.

How to fix it

Find the real heat source. In Activity Monitor, look at the processes below kernel_task. The busiest app after it is the likely cause.
Cool the Mac. Hard surface or stand, nothing on the vents, cooler room. See how to cool down a Mac.
Check the charger side. On Intel MacBooks, charging from the left-side ports while busy was a well-known cause of high kernel_task. Try a different port.
Unplug accessories one by one. A faulty hub, dock or external drive can make kernel_task busy with drivers.
Restart. If it stays high when the Mac is cool and idle, restart and keep macOS updated.

When kernel_task is high and the Mac is NOT hot

Then it is doing real work: heavy disk or network activity, a driver for an external device, or memory pressure (lots of swapping). Check the Memory tab in Activity Monitor for memory pressure in the red or yellow, and the Disk tab for heavy reads and writes.

Don't

Don't try to quit or kill kernel_task. You can't, and it would crash the Mac.
Don't use tools that disable thermal management. They remove the protection that keeps the Mac safe.

Frequently asked questions

Can I quit kernel_task?

No. It is the macOS kernel. It cannot be quit, and you would not want to: it manages memory, hardware and temperature.

Is kernel_task a virus?

No. It is a core part of macOS. A virus would show up as a different process name.

Why is kernel_task using 300% CPU?

Usually because the Mac is hot and macOS is limiting other apps to cool it down. Find the app that heated it, or improve airflow.