Track your Mac's CPU usage over time

Live CPU is easy. CPU over the last hour is the part Apple doesn’t really hand you. If you’re trying to figure out whether the spike that woke your fans was a one-off or a pattern, you need a rolling record — not a single-second snapshot.

Ways to get a CPU history

Activity Monitor’s CPU History window

There’s a hidden gem in Activity Monitor: Window > CPU History (Cmd-3). It opens a small floating chart with stacked bars per core, scrolling right to left.

It’s fine for a few minutes of context, but the window has to stay open and the buffer is short. Close Activity Monitor and the history is gone.

top with logging

Quick and dirty:

top -l 0 -s 5 -stats cpu,command -n 5 | tee cpu_log.txt

That samples every 5 seconds forever, prints to screen, and tees a copy to a file. Ctrl-C to stop. Combine with date in a loop if you want timestamps.

sample / spindump / sysdiagnose

For deeper forensic work, sample PID 10 samples a specific process for 10 seconds and produces a stack-level breakdown. sudo sysdiagnose takes a full system snapshot. These are heavyweight — useful when reporting bugs to Apple, overkill for “was Slack chewing CPU last night.”

A menu bar monitor with built-in history

The most natural fit: something that’s always running and keeps its own history. Beacon stores rolling CPU history and shows it as a sparkline in the bar plus a longer graph when you click.

1. Install Beacon and add CPU to your menu bar.
2. Pick the sparkline display style — you get a tiny rolling chart in the bar itself.
3. Click for the detail panel: longer-range graph plus the top processes contributing to recent spikes.

Because the menu-bar app runs continuously, you can look back at what happened twenty minutes ago instead of starting from “now.”

Patterns worth spotting

When you finally have a history, you start noticing things:

• A spike every 60 minutes — usually a scheduled task (Time Machine, Spotlight, app updaters).
• A spike on resume from sleep — common, normal, lasts a few seconds.
• A slow drift upward over hours — typically a memory leak causing more GC pressure; restarting the offending app resets it.
• A sustained sawtooth — a stuck process retrying something on a loop.

Once you can see the pattern, you can usually map it to a cause. Without history, every problem looks instantaneous and mysterious; with history, it’s just a habit your Mac has.