What keeps a Mac awake
Apps and parts of macOS tell the Mac not to sleep with power assertions. You can list them in Terminal with pmset -g assertions, or in Activity Monitor’s Energy tab, in the Preventing Sleep column. Here is what each name means, whether it’s normal, and what to do about it.
Every name and line on these pages was seen on macOS 27.2.1 on a MacBook Pro with Apple silicon, 11 November 2026.
Apps
The usual reason a Mac stays awake when it shouldn’t.
- Google ChromeGoogle Chrome (browser)“Playing audio”, “Video Wake Lock”, “Capturing” or “Download in progress”.
- ElectronApps built with ElectronAn app built with Electron asked to stay awake; the assertion is named just “Electron”.
- TelegramTelegram (messaging app)“Phone Call” and “Video Playing” while you’re on a call or watching a video.
Tools
Started on purpose, by you, a script or an updater.
macOS services
Part of macOS. Most of these are normal and short.
- coreaudiodSound (the macOS audio service)Keeps the Mac awake while any app plays or records sound, even silence.
- powerdPower management (macOS)“Prevent sleep while display is on”: normal while you use the Mac, gone when the display sleeps.
- WindowServerYour keyboard, mouse and trackpad (macOS)Every key press and mouse move counts as activity, so the idle timer starts again.
- bluetoothdBluetooth (macOS)Short assertions while a Bluetooth device connects or sends input.
- cameracapturedThe camera (macOS)Keeps the Mac awake while an app uses the camera.
- nsurlsessiondBackground downloads and uploads (macOS)Brief “NSURLSessionTask” assertions while apps transfer data in the background.
- clouddiCloud sync (macOS)Short assertions while iCloud syncs.
- mDNSResponderNetwork name service (macOS)“mDNSResponder:maintenance” during short maintenance wakes.
- timedClock sync (macOS)A moment of “com.apple.timed.ntp” while the clock syncs.
The assertion types
The second column of pmset -g assertions. Apps use the “No…Assertion” names, macOS services the “Prevent…” ones; they mean the same.
| Type | What it does |
|---|---|
PreventUserIdleSystemSleep · NoIdleSleepAssertion | The Mac doesn’t go to sleep when idle. The display can still turn off. |
PreventUserIdleDisplaySleep · NoDisplaySleepAssertion | The display stays on, so the Mac stays awake too. |
PreventSystemSleep | System sleep is prevented (on power). Used for updates and by caffeinate -s. |
UserIsActive | Counts as someone using the Mac: the countdown to sleep starts again. Times out. |
SystemIsActive | Short background work, such as a network transfer. Times out. |
MaintenanceWake | Work during a short wake while the Mac sleeps. |
Internal… (InternalPreventSleep, InternalPreventDisplaySleep) | macOS’s own bookkeeping, mostly from powerd. |