How to cool down a Mac without stopping your work

You do not have to quit the build to cool the Mac. You can make it run on the cores that make less heat.

By Andrew Wilson · Updated 2026-10-26

Short answerApple Silicon Macs have two kinds of cores: performance cores (fast, hot) and efficiency cores (slower, cool). Setting a process to background priority makes macOS run it on the efficiency cores. The work continues, takes longer, and the chip runs several degrees cooler. In a WhoIsCooking test the same render ran at 64°C at full speed and 50°C on efficiency cores.

Why this works

Every M-series chip combines performance cores and efficiency cores. When many processes ask for full speed, macOS puts them on the performance cores, which draw the most power and produce most of the heat. Processes marked as background work are scheduled onto the efficiency cores. The same job takes longer, but the chip's temperature and fan noise drop.

Method 1: start a command in background mode

taskpolicy -b npm run build
taskpolicy -b ffmpeg -i input.mov output.mp4

taskpolicy -b launches the command with background scheduling. Use it for long builds, renders and test runs that you do not need finished instantly.

Method 2: lower an already running process

Find the process ID in Activity Monitor (or with ps), then:

taskpolicy -b -p 12345

Replace 12345 with the process ID. To undo it, quit the process or use taskpolicy -B -p 12345. Remember that an AI agent can start dozens of new processes every minute, so doing this by hand only helps for a moment.

Method 3: one click for everything

WhoIsCooking automates the same idea. Press Cool down my Mac and it moves every user process over 2% CPU to the efficiency cores, then checks again every 5 seconds so new processes (the ones your agent just started) are caught too. It shows the result as "55°C → 48°C · 13% cooler". Full speed puts everything back, and quitting the app restores all processes.

What it cannot cool

GPU work (for example games and some video effects) is not affected by CPU core placement.
WindowServer and Apple system processes should be left alone, so tools like this skip them.

Other things that help

Use Low Power Mode (System Settings → Battery) for long jobs.
Keep vents clear and use a hard, flat surface or a laptop stand.
Reduce parallelism in your tools (fewer test workers, lower build jobs).

Frequently asked questions

Does running on efficiency cores slow my work down?

Yes, somewhat. The job takes longer, but it keeps running, uses less power, and produces less heat and fan noise.

Is taskpolicy safe to use?

Yes. taskpolicy is a built-in macOS tool that sets a process's scheduling class. It does not kill or freeze the process, and the setting ends when the process ends.

Which Macs have efficiency cores?

All Apple Silicon Macs (M1 and later) have a mix of performance and efficiency cores. Intel Macs do not.