How to see which app is using the most CPU on a Mac

27 October 2026 · 6 min read

To see which app is using the most CPU on a Mac, open a list of running processes and sort it by the CPU column, highest first. The app at the top is the one using the most processor right now. Watch it for several seconds before you act, because CPU use jumps around, and one spike means little while a figure that stays high means a lot.

This post covers how to get that list, how to read the CPU figure, why one app can be spread over many rows, and what to do once you know who it is.

Get a list sorted by CPU

Foreman is built for this. Press Control-Shift-Escape from any app, the same keys as Task Manager on Windows, and the Processes page opens. Apps, background processes and macOS’s own processes are listed in separate sections. There is a CPU column, and clicking its header sorts the list by it. Each app’s figure is a share of the whole Mac, and above the column Foreman shows the Mac’s total, so you can see how busy the Mac is overall and then which rows account for it.

Foreman also puts a live readout in the menu bar. Click it and a panel opens with a “Using the most” list that you can switch between CPU and Memory, with End Task. That is the quickest look when you only want the name of the app.

In Terminal, the built-in top command does the same job. Type top -o cpu and press Return. It lists processes with the busiest at the top and updates every second or so. Press q to quit. It shows raw process names, so you will meet names like mds_stores and WindowServer that mean nothing until you look them up. Foreman gives macOS’s common ones plain names, with the real name beside them in grey.

How to read the figure

CPU use is a share of the processor’s time. A few things trip people up.

The same number can mean different things in different tools. top counts each processor core as its own 100, so a busy app on a Mac with eight cores can read 300 or more. In Foreman, each app’s CPU figure is a share of the whole Mac, with the Mac’s total above the column. Compare rows within one tool, not with a number you read somewhere else.

One reading is a photograph, not a trend. Apps burst. A page loading, a file saving or a window opening can send an app to the top of the list for a second and then drop it. Look at the list for five to ten seconds. The app that stays at or near the top is the one that matters. If it keeps coming back, that is a pattern worth chasing.

A high figure is not automatically a problem. An app that is exporting a video or compiling code should use a lot of processor, and that is the Mac doing the job you asked for. It becomes a problem when an app uses a lot while you are doing nothing with it.

Zero is also normal. Most processes, most of the time, sit at nothing. Do not worry about rows at the bottom.

Helpers add up under their app

Many apps are not one process. A browser starts a process per tab, plus helpers for networking and graphics. Editors, chat apps and design tools run helpers too. In a raw list, the CPU of such an app is scattered over a dozen lines, and the app’s own line can look quiet while its helpers are busy.

Foreman adds an app’s helpers together under one row, and the row opens to show them. When you sort by CPU, the app’s row already carries the total, and you open it to see which helper is responsible. This is the step that finds the one busy tab in a browser, as the post on telling if one browser tab is slowing down your Mac shows.

Copies of the same background program share a row, with a count, for example “Spotlight file reader (4)”. That row is the cost of all the copies together, so read it as one job, not four separate problems.

What the usual names mean

When the top of the list is not an app you opened, it is usually one of a few macOS processes. A few are worth knowing, using Foreman’s plain names for them.

Spotlight indexing and Spotlight file reader. Spotlight builds and updates its search index. It runs hard after big file changes or updates and then stops.
Photos analysis and Media analysis. They look through your photos and videos for faces, scenes and text. Photos analysis runs mostly while the Mac is idle.
Time Machine backup. A backup in progress.
Window Server. It draws everything on screen. It is busy when you have many windows, several displays or a lot of animation.
macOS kernel. The core of macOS. High CPU here often means the Mac is slowing itself down to stay cool. Do not try to end it; Foreman does not offer to.

These are macOS doing its housekeeping, and ending them rarely helps, since macOS starts many of them again by itself. Wait for them to finish, and check back later. If one that runs under your account, such as Media analysis, is in your way, Efficiency Mode (below) can slow it while you work.

What to do once you know the app

Choose the lightest action that works.

If the app is doing something you asked for, such as exporting, let it finish.
If it is busy for no reason, quit it the normal way with Command-Q, so it can offer to save. In Foreman, End Task does the same, and pressing it again within a minute forces the app to quit.
If it is marked Not responding, force quit it. Option-Command-Escape opens macOS’s Force Quit window; Foreman can also force quit from the Process menu or the right-click menu. You lose any unsaved changes.
If you need it open but not right now, use Efficiency Mode in Foreman. In the background the app runs at background priority and in short bursts, with about a quarter of the processor time it would take. It runs at full speed in front or while playing sound. Foreman remembers the setting for that app. How much it helps depends on how busy the Mac is, so treat it as a way to give the foreground work room, and not as a promise of a particular speed.
If it keeps coming back, look at what starts it. An app that opens at login or runs a background helper can be turned off in System Settings, under General, then Login Items & Extensions (called Login Items on macOS 14). The page on stopping apps opening at login has the steps.

One habit worth having

Open the list when the Mac feels slow, not after you have restarted it. A restart clears the evidence. Sort by CPU, wait a few seconds, note the top row, then sort by Memory and note that too. Two names are usually enough to explain it. For a broader walk through, read why your Mac is so slow.

Foreman is free for 24 hours from the first launch if you want to try the list for yourself. It needs macOS 14 Sonoma or later.