How to check CPU and memory use on a Mac
Open Activity Monitor, click the CPU tab to see processor use, and click the Memory tab to see RAM use. The numbers at the bottom of each tab give the summary, and the list above shows which apps and processes are responsible.
CPU
- Open Activity Monitor. It is in the Utilities folder inside Applications, and Spotlight finds it by name.
- Click the CPU tab.
- Read the percentages at the bottom: System is CPU use by macOS processes, User is use by the apps you opened and their processes, and Idle is unused capacity.
- Choose Window > CPU Usage for current activity or Window > CPU History for recent activity.
To put a CPU graph in the Dock, choose View > Dock Icon and then pick a Show CPU option.
Memory
- Click the Memory tab.
- Read the bottom of the window: Physical Memory is the installed RAM, Memory Used is the RAM in use (with App Memory, Wired Memory and Compressed next to it), Cached Files are files kept in unused memory to speed up reopening apps, and Swap Used is space on the startup disk used to swap files to and from RAM.
- Look at the Memory Pressure graph. Apple says green means RAM is used efficiently, yellow means your Mac might eventually need more, and red means it needs more RAM.
Find the app causing it
Click a column heading to sort the list, and click again to reverse it. Type a name in the search field to find a process. Select a process and double click it, or click the Info button, for details. Use the View menu to switch between choices such as All Processes and My Processes. If a process misbehaves, see quitting an app in Activity Monitor.
High use is not always bad
A busy CPU while you export a video is normal. Memory in use is also normal, because macOS uses spare RAM to speed things up. The signs to watch are a red memory pressure graph, or a process that stays high when you are not using it.
For battery use
If the question is power, see which app uses the most energy.
A glance in the notch
NotchStar’s System tool shows CPU, memory, disk and battery rings and a network readout, sampled once a second while the tab is open. It shows totals only, with no per app breakdown, so use Activity Monitor when you need to find which process is responsible.
