kill iOS Simulator from terminal

The proper way to shutdown simulators is xcrun simctl shutdown all.

I don't recommend shutting down simulators by killing CoreSimulator.

Simulator.app is just a viewer (as of Xcode 9). It does not need to be launched and so does not need to be shut down either. It will respond to devices booting and shutting down automatically.

You can also hold down Option when quitting to detach from running simulators without shutting them down. Check the checkbox to make that the default behavior.

Similarly you can hold down Control when closing a window via File, Close to get a similar choice when closing a single simulator's window.

Use killall "iPhone Simulator"

With XCode 6, use killall "iOS Simulator" (thanks @gempewsaw)

With XCode 7, use killall "Simulator" (thanks @Stanislaw)

With XCode 8, killing the Simulator process is sometimes not enough, also need to kill process com.apple.CoreSimulator.CoreSimulatorService (thanks @bensnider)