System Audio
With the Modern recording engine, system audio captures supported audio playing through macOS, such as media playback, meeting sound, and app sound effects. It is useful when the audience needs to hear what the demonstrated app is playing.
Enable System Audio in the recording panel before starting. The Legacy engine does not support system-audio capture, so this control is disabled there; switch back to Modern when the video needs internal playback sound.
System audio and microphone audio are separate sources. Enable a microphone as well when you need narration, and monitor the levels before recording. This setting does not capture audio from an iPhone or iPad device source.
