Activity Monitor explained: what every tab and number means

Updated 3 October 2026 · 2 min read · by MD Kadiwal

Quick answer

Activity Monitor (Applications › Utilities) shows what's running on your Mac. Use the CPU tab to find what's making it hot or loud, Memory to see if you're running out of RAM, Energy for battery drain, and Disk and Network for heavy reading, writing or downloading. Select a process and click the ✕ button to quit it.

Opening Activity Monitor

Press ⌘ Space, type Activity Monitor and press Return. It's also in Applications › Utilities. Each row is a process: an app, or a helper running in the background. Click any column header to sort by it.

The CPU tab

% CPU: how much processor time each process is using right now. Above 100% is normal: it means more than one core.
CPU Time: total processor time since the process started. Big numbers on old processes are normal.
Threads and Idle Wake Ups: how much work a process splits up, and how often it wakes the CPU. Lots of wake-ups can drain battery.
The graph at the bottom shows System (red) and User (blue) load over time, plus how much is idle.

The Memory tab

Memory pressure graph: the most useful number. Green is fine, yellow means macOS is working to make room, red means you need to close something.
Memory Used, Cached Files and Swap Used: macOS deliberately fills spare memory with cached files, so "almost full" is normal. Rising swap with yellow or red pressure is the real warning sign.
Memory column: how much each process is using. Sort it to find heavy apps.

The Energy tab

Energy Impact: a relative score of how much power each app is using right now.
12 hr Power: average energy use over the last 12 hours, handy for finding battery drains that come and go.
App Nap and Preventing Sleep: whether an app is being paused in the background, or keeping your Mac awake.

The Disk and Network tabs

Disk: bytes read and written by each process. Heavy writes during indexing, backups or syncing are normal.
Network: bytes sent and received. Background downloads usually show up as nsurlsessiond, iCloud as cloudd or bird.

Useful tricks

Quit a process: select it and click ✕ in the toolbar, then Quit. Use Force Quit only if it won't respond; unsaved work is lost.
See details: double-click a process (or click ⓘ) to see its parent process, memory and open files.
Show more processes: the View menu switches between My Processes, All Processes and more.
Keep an eye on CPU from the Dock: choose View › Dock Icon › Show CPU Usage (or Show CPU History), and keep Activity Monitor in the Dock.
Look up unknown names in our Mac process glossary before quitting anything you don't recognise.

Questions people ask

What does more than 100% CPU mean?

Each CPU core counts as 100%, so a process using two full cores shows 200%. It's normal for heavy apps.

Is it normal for memory to look almost full?

Yes. macOS uses spare memory for cached files to speed things up. Watch the memory pressure graph instead: green is fine.

What is kernel_task in Activity Monitor?

It's the core of macOS. When it uses lots of CPU, your Mac is usually too hot and is slowing other apps down to cool off.

Is it safe to quit processes in Activity Monitor?

Quitting your own apps is safe, though unsaved work may be lost. Avoid force quitting system processes you don't recognise; look them up first.