GaugeMon
Mac Performance Guide
Check fan speed on a Mac
Short answer
On Apple Silicon Macs, macOS has no built-in command or window that shows fan speed. On Intel Macs, sudo powermetrics --samplers smc includes it. Otherwise you need an app that reads the System Management Controller (SMC). MacBook Air models have no fan at all.
What you can check
Does powermetrics have the SMC sampler here?
powermetrics -h | grep -c smc0On an M4 Max MacBook Pro this prints 0: the sampler is not offered. The powermetrics man page describes the smc sampler as reporting fan speed and temperature sensors "on supported platforms", which in practice means Intel Macs, where it needs sudo:
sudo powermetrics --samplers smc -n 1The IORegistry does not have it either
ioreg -l | grep -ic '"fan'0Whether heat is a problem at all
pmset -g thermNote: No thermal warning level has been recorded
Note: No performance warning level has been recordedWhy you might care
Fans spin up because something is producing heat. If they are loud, the useful question is which process is causing it: top -l 2 -n 10 -o cpu -stats pid,command,cpu answers that. A fan that runs fast with no load, or never runs while the Mac is hot, is worth a visit to Apple Diagnostics or a repair shop.
The easier way: GaugeMon
GaugeMon reads fan speed from the SMC, read-only and without sudo, on both Apple Silicon and Intel Macs that have fans. Show it in the menu bar next to temperature; on a MacBook Air the Fans gauge is simply hidden.
