CPU & energy
Preventing Sleep
Shows which apps are keeping your Mac awake.
What it is
Apps can tell macOS not to sleep, for example while playing a video, downloading or presenting. Activity Monitor's Energy tab has a Preventing Sleep column showing which apps are doing it.
In Terminal, pmset -g assertions lists everything currently preventing sleep, including system services.
Should you worry?
Only if your Mac won't sleep when you expect it to.
What you can do
- Quit the app shown as preventing sleep.
- Check browser tabs playing media.