til/mac/inspect-assertions-preventing-sleep.md

Inspect Assertions Preventing Sleep

The pmset command is for inspecting and manipulating Power Management Settings on MacOS. The -g flag is for getting details. We can get a summary of power assertions with -g assertions. These assertions are ways that the system and display are prevented from sleeping.

A common assertion preventing sleep is the user being active. Another example of an assertion is a program like caffeinate that sets a timeout preventing sleep for a fixed period of time.

Here I activate a 30 minute (1600 second) caffeinate session and then I inspect the power management assertions which shows the details of that assertion as well as two others.

❯ caffeinate -t 1600 &
[1] 98217

❯ pmset -g assertions
2025-11-02 13:20:57 -0600
Assertion status system-wide:
   BackgroundTask                 0
   ApplePushServiceTask           0
   UserIsActive                   1
   PreventUserIdleDisplaySleep    0
   PreventSystemSleep             0
   ExternalMedia                  0
   PreventUserIdleSystemSleep     1
   NetworkClientActive            0
Listed by owning process:
   pid 98217(caffeinate): [0x00045477000194b3] 00:00:03 PreventUserIdleSystemSleep named: "caffeinate command-line tool"
        Details: caffeinate asserting for 1600 secs
        Localized=THE CAFFEINATE TOOL IS PREVENTING SLEEP.
        Timeout will fire in 1597 secs Action=TimeoutActionRelease
   pid 145(WindowServer): [0x00044f2f00099212] 00:00:00 UserIsActive named: "com.apple.iohideventsystem.queue.tickle serviceID:10009be9e service:AppleUserHIDEventService product:CTRL Keyboard eventType:3"
        Timeout will fire in 600 secs Action=TimeoutActionRelease
   pid 80(powerd): [0x00044f2f00019216] 00:22:34 PreventUserIdleSystemSleep named: "Powerd - Prevent sleep while display is on"

See man pmset and man caffeinate for more details.