kernel_task high CPU? Your Mac is cooling itself

What is kernel_task?

kernel_task is a process that belongs to macOS, not an app you opened. Apple says one of its jobs is to help manage the processor’s temperature. You’ll see it in Activity Monitor’s lists like any other process.

Why is kernel_task using so much CPU?

Because something has made the processor hot. When that happens, kernel_task makes the processor less available to the processes using it heavily. In Activity Monitor, that shows up as kernel_task using a large percentage of the CPU, often while the fans are loud.

kernel_task responds to the heat; it doesn’t cause it. Common reasons a Mac gets hot, from Apple’s guidance:

• Demanding work that lasts, such as compressing HD video, playing a graphics-heavy game, or Spotlight indexing after you move your data to a new Mac.
• A warm room. Apple recommends using a Mac laptop where it’s between 10 °C and 35 °C (50 °F and 95 °F).
• Blocked airflow, from a bed, couch, pillow or lap, or something covering the keyboard or the vents.

How do I find what’s making my Mac hot?

Look past kernel_task for the app doing the work.

1. Open Activity Monitor. It’s in Applications > Utilities, or search for it with Spotlight.
2. Click CPU, then click the % CPU column heading to sort the list, busiest first.
3. Look at the apps around kernel_task. The app that stays near the top for minutes is the one making the heat.

At the bottom of the window, System is the share of the processor used by processes that belong to macOS, and User is the share used by the apps you opened. Here User, 71.80%, is far larger than System, 14.60%: your apps are doing most of the work.

What should I do about it?

• Let the work finish, or quit the app. If the app is doing work you asked for, such as a render or an export, kernel_task eases off after it’s done and the processor cools. If you don’t need the app now, quit it from its own menu, saving your work first.
• If the app isn’t responding, select it in Activity Monitor, click the Stop button at the top of the window, then choose Quit. Choose Force Quit only if Quit doesn’t work, because unsaved work in that app is lost.
• Give your Mac air. Use it on a hard, flat surface, such as a table or desk, and keep the vents and keyboard uncovered.
• Leave kernel_task alone. It’s doing its job, and Apple says its activity goes down on its own as the processor cools.

What if kernel_task stays high with nothing running?

Check Activity Monitor’s CPU list again for something working in the background, such as Spotlight indexing, a sync or an app that opens at login. If your Mac still runs warm or its fans keep going during light work, Apple suggests closing the lid and opening it again, or restarting your Mac. On an Intel-based Mac, Apple also suggests resetting the SMC (System Management Controller); MacBook fan loud? What’s making it spin up has the steps. If it continues, contact Apple or an Apple Authorized Service Provider.

Questions people also ask

Is kernel_task a virus?

No. kernel_task is part of macOS, and Apple describes it as helping manage the processor’s temperature. High kernel_task CPU is a sign that the processor is hot.

Does kernel_task slow my Mac down?

It can, for a while and on purpose. It makes the processor less available to the processes using it heavily until the processor cools, so a busy app may run slower in the meantime.

Why are my fans loud when kernel_task is high?

Both respond to the same heat. The fans move air to cool your Mac, and kernel_task holds the processor back. Why is my MacBook getting hot? explains what to do about the heat.