Which app is slowing down my Mac? How to find it

How do I find the app using the most CPU?

The CPU list shows how much of the processor each app is using right now.

1. Open Activity Monitor. It’s in Applications > Utilities, or search for it with Spotlight.
2. Click CPU at the top of the window.
3. Click the % CPU column heading to sort the list, busiest first. Click the arrow in the heading to reverse it.
4. Watch the top of the list for a minute. Apps jump up for a moment when they open or save, which is normal. An app that stays near the top is doing sustained work.

Activity Monitor counts each processor core as 100%, so an app working on several cores can show more than 100%, as Blender does here. If you’re looking for one app, type its name in the search field at the top right of the window.

How do I find the app using the most memory?

Click Memory in Activity Monitor, then click the Memory column heading to sort by it.

Before you quit anything, look at the Memory Pressure graph at the bottom of the window. Green means your Mac is using its memory efficiently, even if most of it is in use. Yellow or red means your Mac is short of memory, and the apps at the top of this list are the ones to close first.

Why does one app show up many times?

Many apps do their work in several processes: helpers with names such as “Helper” or “Renderer”, each in its own row. To see which app each one belongs to, choose View > All Processes, Hierarchically. Activity Monitor then shows each process under the one that started it.

What should I do about the app?

• If it’s doing work you asked for, such as an export, a render or a large download, let it finish. It eases off on its own.
• If you don’t need it right now, quit it from its own menu. Save your work in it first.
• If it isn’t responding, select it in Activity Monitor, click the Stop button at the top of the window, and choose Quit. Choose Force Quit only if Quit doesn’t work, because anything unsaved in that app is lost.
• If it happens every day, check whether the app opens at login: Apple menu > System Settings > General > Login Items & Extensions.

What if no app stands out?

When no app stays at the top, the slowdown is usually somewhere else: a startup disk that’s nearly full, a Mac that’s too hot, or memory pressure that stays yellow or red with many apps open. Why is my Mac slow? walks through each one.

Questions people also ask

Why is kernel_task using so much CPU?

kernel_task is part of macOS, not an app. Apple says one of its jobs is to keep the processor from getting too hot, by making it less available to processes using it heavily. Look for the app working hard, and give your Mac room for air.

Is it safe to quit an app from Activity Monitor?

Quit is as safe as quitting from the app’s own menu. Force Quit closes the app at once, so any work you haven’t saved in it is lost.

Why is my Mac slow when nothing is open?

Something may be running without a window, such as an app that opens at login or a sync in the background. In Activity Monitor, sort by % CPU to see it, and check Login Items & Extensions in System Settings.