Which app is using my CPU or memory? How to check on a Mac

Activity Monitor answers this question on every Mac, but its figures are easy to misread: % CPU passes 100%, one app appears as twenty processes, and memory looks full when nothing is wrong. Below are the steps on macOS 26 Tahoe, what each figure means, and the Terminal equivalent. If the real problem is a Mac that feels slow, start with why your Mac is so slow, which covers causes Activity Monitor does not show, such as a full disk.

How to check CPU and memory usage in Activity Monitor

1. Open Activity Monitor. Press ⌘Space, type Activity Monitor and press Return, or open Applications > Utilities.
2. Sort the CPU tab. Click CPU in the toolbar, then click the % CPU column heading. Click it again if the smallest figures are on top.
3. Read the totals at the bottom. Apple’s guide defines three totals. System is CPU used by processes that belong to macOS, User is CPU used by apps you opened and their processes, and Idle is what is not being used (Apple: CPU activity, macOS 26). For a graph over time, choose Window > CPU History.
4. Sort the Memory tab. Click Memory, then click the Memory column heading to put the largest process first.
5. Check Memory Pressure. The graph at the bottom of the Memory tab says whether memory is short. Apple’s guide: green means the Mac is using all of its RAM efficiently, yellow that it might eventually need more, red that it needs more RAM (Apple: does your Mac need more RAM).
6. Find the app behind a process. Type a name in the search field to filter the list, or double-click a process to get information about it (Apple: process information, macOS 26). View > All Processes, Hierarchically shows which process started which.

To quit something you find, select it, click the Stop button in the toolbar and choose Quit.

Why % CPU goes past 100%

% CPU is how much processor time a process uses, where one fully busy core counts as 100%. On an 8-core Mac the scale runs to 800% (The Eclectic Light Company), so on a 10-core M4 it runs to 1,000%. A process at 170% is keeping almost two cores busy, which is normal for a build, an export or a heavy web page.

Two things make the figure less precise than it looks. Apple silicon has performance and efficiency cores, and the same article notes that Activity Monitor makes no distinction between them, so 100% on efficiency cores is less work than 100% on performance cores. And the total of the column is not a percentage of the whole Mac; the System, User and Idle figures at the bottom are.

On a 16 GB Apple M4 Mac with 10 cores, one Chrome renderer process showed 171% CPU, and at the same moment mediaanalysisd, the macOS process that analyses photos and media, showed 97% (a ps snapshot taken on October 1, 2026).

What the Memory tab’s figures mean

Below the Memory Pressure graph, Activity Monitor splits memory into a few figures. The middle column follows Apple’s macOS 26 guide, slightly shortened (Apple: memory usage, macOS 26); the last says what each figure tells you.

Memory pressure is the figure that combines these. Apple says it is “determined by the amount of free memory, swap rate, wired memory, and file cached memory”. The glossary has longer entries for memory pressure, compressed memory and swap used.

Why one app shows up as many processes

A process is simply a running program, in the operating-system sense (Operating Systems: Three Easy Pieces), and Activity Monitor gives every process its own row. Helper processes are separate processes an app starts for part of its work, such as rendering a web page or running a plugin. If one crashes, the rest of the app keeps going. Browsers and apps built on browser engines do this most, for example Chrome, Slack, Visual Studio Code and other Electron apps. Each piece shows up as its own row, such as Google Chrome Helper (Renderer).

In the same ps snapshot on the 16 GB M4 Mac, 26 of the 531 running processes belonged to Chrome. Activity Monitor lists every one of them separately, so the app’s real total is the sum of its rows. Sorting by % CPU or Memory can put a single helper on top while the app as a whole uses far more. View > All Processes, Hierarchically places children under their parent, which helps, but each row still shows only its own figures.

Check CPU and memory usage in Terminal

Terminal gives the same lists without opening a window, which helps over SSH or in a script. This watches processes sorted by CPU; press q to quit.

top -o cpu

This sorts by memory instead.

top -o mem

For a one-off list of the ten busiest processes, use ps. Here -c shortens the names, -r sorts by CPU and -m by memory, and RSS is resident memory in kilobytes.

ps -Aco pid,pcpu,rss,comm -r | head -n 11
ps -Aco pid,pcpu,rss,comm -m | head -n 11

The top manual describes mem as the physical memory footprint of the process (top(1)), and ps documents -r and -m as sorting by current CPU usage and by memory usage (ps(1)). For memory as a whole, memory_pressure prints the system-wide free percentage and sysctl vm.swapusage prints swap in use.

When high memory use is fine, and when it is not

High Memory Used is normal. macOS fills spare RAM with cached files and compresses idle memory instead of leaving RAM empty, so a Mac with 16 GB will often show close to 16 GB used. That costs nothing as long as the pressure graph is green.

It becomes a problem when:

• Memory Pressure stays yellow or red with only your usual apps open.
• Swap Used keeps growing over hours instead of settling.
• One app’s Memory figure only rises, even when you are not giving it more work. That is the pattern of a memory leak, and relaunching the app is the fix.

The steps to get memory back, and why cleaner apps do not help, are in how to free up RAM on a Mac.

Where Orcylo fits

Activity Monitor answers “what is busy right now” one process at a time. We make Orcylo, a menu bar monitor for macOS 15 and later that adds up each app’s helper processes into one row with its CPU, memory, GPU, power, disk and network. It keeps 30 days of per-minute history, so you can see when an app started growing, and alerts you when an app burns CPU for minutes or its memory keeps growing. See the features, read how it compares with Activity Monitor, or browse the best Activity Monitor alternatives.

How we checked

Every menu path and label was checked against Apple’s macOS 26 Tahoe Activity Monitor guide on October 1, 2026. The Terminal commands were run the same day on a 16 GB Apple M4 Mac with 10 cores, and the figures quoted above come from that run. Quotes from Apple and the manual pages went through a fact check against the linked pages.