Find out what's stopping your Mac from sleeping — via SS64

Commandlow riskmacOS 14 Sonoma and later

If your Mac won't sleep, or the display stays on, an app is usually holding a 'power assertion'. One read-only command lists every app currently blocking sleep, and Activity Monitor shows the same thing in a column.

Takes effect right away

The easy way

  1. Run the command. The summary at the top shows which kinds of sleep are being blocked (a value of 1), and the list underneath names the process holding each one.
  2. The friendly way: open Activity Monitor, click the Energy tab, and check the Preventing Sleep column.
  3. Bonus: pmset -g batt shows the battery level and whether you're on the charger.

Command

Run in Terminal (Applications › Utilities).

pmset -g assertions
These commands only read information; they don't change anything.

Sources

Source reviewed
2026-11-02
Link checked
2026-11-02
Tested hands-on
Not by Oddbyte.Me

Oddbyte.Me hasn't tried this on every macOS version, so keep the undo handy.

sleepwon't sleeppmsetassertionsbattery draininsomnia

More in Performance & Power

Check memory pressure, not 'free RAM' — via Apple Support

Tricklow risk

A Mac that shows almost no free memory is usually fine: macOS keeps recently used files cached in RAM so apps reopen faster. The number that matters is the Memory Pressure graph in Activity Monitor, which combines free memory, swap and cached files.