Activity Monitor shows what every running app and process is doing on your Mac. When the Mac feels slow, gets hot, spins its fans, or drains battery quickly, it is the fastest built-in way to see the cause instead of guessing.
This guide applies to Activity Monitor on any recent macOS version.
Does This Affect You?
Use this when one app seems frozen, the whole Mac is sluggish, or you want to identify a process using too much CPU, memory, battery, disk, or network bandwidth.
Open Activity Monitor and Sort by Usage
- Press Command + Space, type Activity Monitor, and press Return. You can also open it from Applications > Utilities.
- Select the CPU tab first.
- Click the % CPU column to sort from highest to lowest.
- Watch the list for several seconds because some processes spike briefly and then calm down.
- If CPU looks normal, switch to Memory and sort by Memory to find apps using large amounts of RAM.
On multi-core Macs, a single process can show more than 100 percent CPU. If one app stays around 100-150 percent or higher, it is worth investigating.
Quit or Force Quit a Problem App
- Select the process in Activity Monitor.
- Click the X stop button in the toolbar.
- Choose Quit first if the app may still respond.
- Choose Force Quit only if normal Quit fails.
- Confirm the action.
Force Quit closes the app immediately and can discard unsaved work, so treat it as a recovery step rather than a normal close button.
Other Activity Monitor Tabs
Energy
Use Energy to find apps hurting battery life. The Significant Energy column can reveal apps that used lots of power recently.
Disk and Network
If CPU and memory look fine, check Disk for heavy reads and writes or Network for large uploads and downloads. Time Machine, Spotlight, and cloud sync apps often appear here.
Process Details
Double-click a process to view more information, including CPU history, memory footprint, and open files. This helps identify unfamiliar items before quitting them.
System and User Load
The bottom of the CPU tab shows overall system and user CPU load. It helps distinguish one noisy app from a Mac that is genuinely under heavy load.
Sources
- Apple Support: Use Activity Monitor on Mac
- Apple Support: Force quit an app on Mac
- Apple: Activity Monitor tabs and process information