How to see which process is using the most CPU or memory on a Mac
Open the notch, choose Disk, then Monitor, and leave it on Usage. Two columns list the busiest processes by CPU and the ones using the most memory, five of each. A third column lists listening ports. It refreshes about every three seconds while you look at it.
Steps
- Open the notch and choose Disk, then Monitor.
- Press Usage if Ports is showing.
- Read Busiest (CPU), which gives each process name and a percentage, and Most memory, which gives the memory in a size such as megabytes.
- Keep the notch open (the Keep open button in the header) while you reproduce the problem, such as starting a build or opening a heavy page.
- Watch which name stays on top.
Reading the numbers
The numbers come from the system’s ps tool. The memory figure is resident memory, which is what a process holds in RAM right now. Neither tells you why a process is busy.
Pair it with the overall gauges
The System tab shows total CPU, memory, disk and battery as rings, plus network speed, sampled each second. It answers “is my Mac busy?”. The Monitor answers “which process?”. Use the gauges first, then Monitor for the name. The build use case puts both together.
Limits
- Top five only. If the culprit is sixth, you will not see it.
- Snapshots, not history. There is no graph over time and nothing is logged.
- No per process network or energy figures.
- No grouping. Several helper processes of one app appear as separate rows.
- Name only. It shows no icon and no way to open the app from the row.
- You can stop only listening servers, from the Ports view. The Usage view has no quit button.
- Sampling stops when you leave the section, which keeps NotchStar itself quiet.
If the busy process is an app you recognise, use that app’s own quit. If you do not recognise the name, search for it before you act, since many background processes are part of macOS. The Disk page explains the other sections, including how to see what a port belongs to.
