How do I see what's using CPU on my Mac?

Open Activity Monitor, pick the CPU tab and sort by % CPU. In Terminal, ps -Ao pid,pcpu,comm -r | head -11 shows the top ten.

Dhiru · dev watch

What's using my CPU on Mac? How to find it and stop it

Open Activity Monitor (Spotlight, then type Activity Monitor), choose the CPU tab and sort by % CPU. The top rows are what's working hardest. Select one and press the ⓧ button to quit it.

From Terminal, the top ten:

ps -Ao pid,pcpu,comm -r | head -11

Then kill <PID> to stop one. Leave processes you don't recognise that belong to macOS (kernel_task, WindowServer) alone; they're part of the system.

A common culprit for developers is a dev server or file watcher (webpack, Vite, tsc --watch, Docker) left running in a terminal you forgot about.