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How to see CPU usage on a Mac

Updated 25 October 2026 · 4 min read

How to see CPU usage on a Mac with Activity Monitor, top and ps, and how Orrel totals each app's helper processes and flags what dev tools left running.

A Mac that has gone slow, a fan that will not settle, a battery that drains in an afternoon: the usual question is which app is responsible. macOS answers it with Activity Monitor, and Terminal answers it in one line.

Activity Monitor

Press ⌘Space, type Activity Monitor and press Return. It also lives in Applications › Utilities. Click CPU at the top of the window, then click the % CPU column header so the busiest processes come first.

• % CPU is the share of one core the process is using. On a Mac with many cores, a busy process can show well over 100%.
• CPU Time is how much processor time it has used since it started, which shows the slow, steady consumers that never top the list.
• The bottom of the window shows System (macOS's own processes), User (apps you opened and what they started) and Idle, plus a CPU Load graph, for the Mac as a whole.

View › All Processes shows everything, including macOS's own processes; My Processes narrows it to yours. To stop something, select it, click the stop button (✕) in the toolbar and choose Quit, or Force Quit if it does not respond.

Keep CPU on screen

• In the Dock. In Activity Monitor choose View › Dock Icon and pick Show CPU Usage or Show CPU History. The Dock icon becomes a live graph while Activity Monitor is open.
• In a small window. Window › CPU Usage shows a meter for each core; Window › CPU History shows recent activity. Both stay open with the main window closed.

The Energy tab

On a laptop, the Energy tab is often more useful than CPU. Energy Impact combines CPU, graphics, network and disk use into one relative figure, and the 12-hour Power column shows which apps have used the most over the day. It also shows whether an app is preventing sleep.

In Terminal

top is the live, text version of Activity Monitor:

top -o cpu

Processes are sorted by CPU and the list updates every second. Press q to quit. For a single snapshot of the ten busiest processes, take two samples, because the first one has no previous reading to compare against:

top -l 2 -o cpu -n 10 -stats pid,command,cpu | tail -n 11

ps gives a quick list sorted by CPU:

ps -Arc -o pid,%cpu,comm | head -n 11

On macOS, the ps figure is a decaying average over roughly the last minute, so it moves more slowly than top or Activity Monitor.

Reading what you find

• Many processes, one app. Browsers and Electron apps run a helper for each tab, extension or window. The app's real cost is the total, not the top line.
• Indexing. mds_stores and mdworker are Spotlight indexing. They are busy after an update or when many files change, and settle on their own.
• kernel_task. macOS uses it to slow other work when the Mac is warm. It is a symptom of heat, not a cause.
• Things you forgot. A dev server, a build watcher or a script started in a terminal you have since closed can keep a core busy for days.

How Orrel does it

Orrel's Running screen shows CPU and memory for the whole Mac at the top, with a short history graph, then three lists:

• Apps. Every app with all its helper processes added together, so a browser with forty tab processes is one row with one total. Sort by CPU or memory, and quit an app from its row. A second press forces it.
• Started by your tools. What each terminal, editor and coding agent session (Claude Code, Codex and others) started, grouped by session, with the CPU and memory of each group.
• Left running. Processes whose terminal or agent has quit, flagged so you can stop them, with everything they started, at once.

Per-process figures are a share of one core, as in Activity Monitor. The screen refreshes every two seconds while it is open. Localhost servers are listed too, with the project and the tool that started them; see how to find what is running on a port. The menu bar item shows those servers and any processes left running without opening the window.

Where Orrel stops

Orrel reads and stops your own processes only. macOS services and processes running as root or another user, including kernel_task and WindowServer, are not listed, so Activity Monitor with All Processes remains the place to see everything. Orrel has no Energy, Disk, Network or GPU view, no per-core graphs, and it does not put a CPU figure in the menu bar. macOS apps cannot be quit from Orrel.