Beacon guide

How to kill a runaway process on Mac

When an app pegs your CPU or eats all your RAM, you need to kill it fast. Here are the GUI and Terminal ways, plus when to use each.

4 min read

Something is wedged. A browser tab, a renderer, a stuck Electron app — whatever it is, it’s pinning a core at 100% and your fans are climbing. You want it gone, and a regular Cmd-Q isn’t doing it. Here are the reliable ways to kill a process on macOS.

The fast options

Force Quit (Cmd-Option-Escape)

This is the panic-button shortcut every Mac user should know. It pops a small window listing running apps; pick the offender, hit Force Quit. Works for anything with a Dock icon.

It doesn’t cover background processes, helper apps, or anything without a visible UI — for those, you need one of the next two.

Activity Monitor

Open Activity Monitor, sort by %CPU or Memory, find the rogue, click the X in the toolbar, choose Force Quit. This works on every running process, including the background ones Cmd-Option-Esc won’t show you.

Terminal: kill, killall, pkill

For anything terminal-side or anything that won’t die through the GUI:

  1. Find the PID: ps aux | grep ProcessName or pgrep -fl ProcessName.
  2. Try a graceful stop first: kill PID. This sends SIGTERM and lets the process clean up.
  3. If it ignores you after a few seconds: kill -9 PID. SIGKILL — the kernel reaps it immediately.
  4. Want to kill every instance by name? killall "App Name" or pkill -f pattern.

A note on kill -9: it doesn’t let the process save state, flush buffers, or run shutdown handlers. Reach for kill (no -9) first, only escalate if needed.

Finding the right thing to kill

The hard part is usually identifying the runaway, not killing it. A few approaches:

Beacon fits this last role. Its menu-bar CPU readout updates roughly once a second, and clicking the icon shows the top CPU users right there.

  1. Install Beacon and enable the CPU readout in Settings > Menu Bar.
  2. When CPU spikes, click the icon — you see the top three processes immediately.
  3. Click a process to jump to it in Activity Monitor for the kill, or grab the PID and use kill in Terminal.

The faster you spot a runaway, the less battery, heat, and time it costs you. The killing part is easy — the noticing is what gets you.

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