Performance
Why kernel_task uses so much CPU on a Mac
Updated · Applies to macOS 14 and later
kernel_task isn't the problem. When the CPU gets too hot, macOS uses kernel_task to take CPU time away from whatever is working it hard, so it shows high usage. Find the app that's using lots of CPU, quit or pause it, and kernel_task drops back once the Mac cools.
What kernel_task is doing
kernel_task is macOS itself. One of its jobs is managing heat: when the processor gets too hot, it takes processor time away from apps that are using it heavily, which lets the chip cool down. In Activity Monitor that time shows up as kernel_task’s CPU usage.
Apple is clear that kernel_task responds to heat; it doesn’t cause it. And the Mac doesn’t have to feel hot for it to happen. When the temperature drops, kernel_task’s usage drops too.
Find what’s heating the Mac
- Open Activity Monitor (in Applications → Utilities) and click CPU.
- Click the % CPU column to sort. Ignore kernel_task and look at what’s under it.
- Watch for an app that stays high while you’re not using it: a stuck browser tab, a build, a video export, or an app’s helper process.
- Quit it normally, or select it and click the ⊗ button to quit it from Activity Monitor.
How to find which app is slowing down your Mac goes through this in more detail, including apps split across several helper processes.
Other things that make a Mac warm
- Blocked vents: using a MacBook on a bed or cushion, or dust in a desktop Mac’s vents.
- A hot room or direct sunlight.
- Charging while working hard, which adds heat of its own.
- Several external displays, which keep the graphics working harder.