App Nap

Quick answer

App Nap is a macOS feature that slows down apps you are not using, such as apps whose windows are hidden and that are not playing audio. The App Nap column in the Energy tab of Activity Monitor shows which apps are napping right now.

When an app naps, macOS lowers its priority for CPU time, fires its timers less often, and limits how fast it can read and write to disk while other apps need it. The app wakes up and returns to normal as soon as you switch to it or it has work to do.

Apple's developer documentation lists the conditions: the app is not in the foreground, has not recently updated a visible part of a window, is not playing audio, and has not asked macOS to stay active. Apps can opt out when they need to keep working in the background.

How to see which apps are in App Nap

Open Activity Monitor and click the Energy tab. The App Nap column shows Yes for apps that are napping. If you click an app to bring it forward, the value changes back to No.

Why an app never shows App Nap

An app that plays audio, downloads files, or keeps a visible window updating is not eligible. Some apps also tell macOS they are doing user work, which keeps them out of App Nap. Background processes without windows often do not show App Nap at all.

Should you turn off App Nap?

For almost everyone, leave it on. It only slows apps that are hidden and idle, and it saves battery by giving them less CPU time and firing their timers less often. Well built apps tell macOS when they are doing work you asked for, such as a download or an export, and stay awake on their own.

It can get in the way with older apps, or apps that do not follow Apple's guidance, when they run a long task in the background. If a task seems to slow down whenever you switch away from the app, App Nap is a likely cause.

There is no App Nap switch in System Settings. Some older apps show a Prevent App Nap checkbox in the Finder Get Info window. Apps built for newer versions of macOS do not show it, and the choice is left to the developer.

How to keep one long task running at full speed

Start the task, then open Activity Monitor and click the Energy tab.
Switch to another app and watch the App Nap column for the app running the task.
If it changes to Yes and the task slows, keep a window of that app visible on screen, where its progress can update. Do not minimize it or hide it.
Check the app's settings for an option to keep working in the background, and update the app.
If the problem stays, tell the developer. Apple gives developers a way to keep an app active while it does work the user started.

How to see App Nap working

You can watch App Nap take effect in Activity Monitor. Pick an app that is open but idle, such as a chat or mail app.

In the CPU tab, note the app's % CPU and how fast its Idle Wake Ups value changes.
Hide the app with Command-H, or cover its windows completely with another app.
Wait a little, then check the Energy tab. When the App Nap column shows Yes, go back to the CPU tab.
Compare the numbers. Its timers now fire less often, so wakeups and CPU use usually drop.
Click the app in the Dock. The App Nap column returns to No and the app runs at full speed again.

App Nap vs Low Power Mode vs sleep

These are often confused, but they work at different levels.

App Nap works on one app at a time, automatically, while that app is hidden and idle. The rest of the Mac runs at full speed.
Low Power Mode works on the whole Mac. Apple says it reduces energy use to increase battery life. You turn it on in System Settings > Battery.
Sleep stops almost everything until you wake the Mac. Apps that keep the Mac awake appear in the Preventing Sleep column instead.

Questions people ask

What does App Nap mean in Activity Monitor?

It shows whether macOS has slowed down that app because you are not using it. Yes means the app is napping and using fewer resources.

Does App Nap close or pause the app?

No. The app keeps running and its data stays in memory. macOS only gives it less CPU time and fewer timer wakeups until you use it again.

Should I turn off App Nap?

For most people, no. It helps the apps you are using stay responsive and can reduce background activity. Apps that must keep working in the background can opt out on their own.

Can App Nap slow down a download or an export?

It can, if the app does not tell macOS it is doing work for you. Most current apps do. Keeping a window visible where the app shows its progress usually keeps it out of App Nap.

Is there a setting to turn off App Nap?

Not in System Settings. Some older apps have a Prevent App Nap checkbox in Finder's Get Info window. For newer apps, the developer decides.

Does App Nap work on desktop Macs too?

Yes. App Nap is not limited to laptops. The App Nap column appears in the Energy tab on desktop Macs as well.

Looking for something better than Activity Monitor? See the best Activity Monitor alternatives for Mac, or browse every term in the glossary.