macOS processes › Core system
What is UserEventAgent on Mac?
UserEventAgent watches for system events, like a network change, a device being plugged in, or the Mac going to sleep, and starts or notifies the services that care. One copy runs for the system and one for your user account.
What it does
It loads small Apple plug-ins from /System/Library/UserEventPlugins, each listening for a kind of event, such as Bluetooth, Bonjour, input devices or captive Wi-Fi networks. When an event happens, it can trigger jobs that launchd was holding until that event. It mostly coordinates, so its own work is usually tiny.
Why it gets busy
- A stream of repeated events, such as a USB or Bluetooth device that keeps disconnecting and reconnecting.
- Network changes in quick succession.
- Waking from sleep, when many events fire together.
Why is UserEventAgent using so much CPU?
UserEventAgent is busy when events keep firing, most often from a device that keeps disconnecting or a network connection that keeps dropping. Fix that device or connection and it calms down.
Is it safe to quit?
macOS relaunches it, but events that happen while it's gone can be missed, so some services may not start when they should.
How to calm it down
- Unplug USB devices and hubs one at a time to find one that keeps reconnecting.
- Check for an unstable Wi-Fi or Ethernet connection.
- If unplugging devices doesn't help, restart the Mac so it reloads its plug-ins from scratch.
In SystemWatch
SystemWatch's History shows whether UserEventAgent spikes when you plug in a dock or device, which points to the hardware to check.
