How to watch CPU and memory while a build runs on a Mac

Coding Published 4 November 2026

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Start the build, open the notch, choose System and press Keep open. The gauges show CPU, memory and disk as percentages with network speed beside them, sampled once a second. To find which process is responsible, switch to Disk, then Monitor.

Steps

Start the build or test run in your terminal or editor.
Open the notch and choose System. The rings show CPU, Memory and Disk, plus Battery on a Mac that has one and Network download and upload rates.
Press Keep open in the header, so the notch stays up while you work in other windows.
Watch the colours. Usage turns orange above 65 percent and red above 85 percent. A battery turns red when low and green while charging.
If the CPU stays red, choose Disk, then Monitor, to see the five busiest processes by CPU and by memory.
When the build ends, press Unpin.

Time the build

Start a stopwatch in Timers before the build. It keeps counting while the notch is closed, and you read it by opening the notch. When you change something and rebuild, you can compare the two times. It is not a benchmark, since a busy Mac gives noisy results. Run each case a few times and write the numbers down yourself, because the stopwatch keeps no history.

What the numbers mean

Memory is active, wired and compressed memory against your Mac’s total. The disk ring is how full the disk is, not how busy. Network speeds come from WiFi and Ethernet, and VPN or other virtual interfaces are left out so traffic is not counted twice. The first network reading appears after the second sample.

Limits

Totals only. The System tab has no per app breakdown.
No graph or log. You see now, not what happened five minutes ago.
Not a profiler. It will not tell you why a compile is slow.
Temperature and fan speed are not shown.
Per core load is not shown.
Pinned means in the way. A pinned notch sits above other windows at the top of the screen, so unpin it when done.

For deeper work use Instruments or Activity Monitor. These gauges are for a glance. See the System page for the full list.

Quick answers.

Does the System tab show which app is using the CPU?

No. It shows totals. Use Disk, Monitor, Usage to see the busiest processes.

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Does watching make my Mac slower?

It reads a few system counters once a second, only while the tab is on screen.

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Keep reading.

CPU, memory, disk, battery and network: Live CPU, memory, disk, battery and network speed gauges in your Mac notch. Sampling only runs while the tab is open, so it stays light.
Disk space, duplicates, apps and cleanup: See free space, find big folders, duplicates and app leftovers, compress media and clean caches from your Mac notch. Everything goes to the Trash.
How to see which process is using the most CPU or memory on a Mac: The NotchStar Disk tab, Monitor, Usage shows the five busiest processes by CPU and by memory, refreshed every few seconds. No per app history.
Timer, stopwatch and Pomodoro in the notch: A timer, stopwatch and Pomodoro with session tracking, always one hover away in the Mac notch. It keeps counting while the notch is closed.

Put your notch to work.

Buy it once for $4, activate it in a minute, and keep it. Not sure yet? Try every tool in the browser on the home page, or install the 7 day trial.

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