Record your microphone in a Mac screen recording

Add your voice to a Shoverlay screen recording with the microphone track, separate from the Mac’s internal audio.

The microphone track is your voice. System audio is the sound the Mac is already playing. Turn on only the microphone when the clip should include you and not the other audio.

Turn the microphone on

Start the recording region: an area, a window, or the full screen.
In Recording settings, turn on the microphone. Leave system audio off if you do not want app sound in the file.
Allow Microphone for Shoverlay when macOS asks. Quit and reopen Shoverlay after you allow it.
Use MP4 or MOV so the voice has a soundtrack to live in.

A mono mix is there if you want the channels combined. It does not replace the choice of which input is on.

If your voice is missing

Microphone permission is off, the track is off in Recording settings, or the input device in System Settings → Sound is not the mic you spoke into. GIF and animated WebP are the wrong format for a voice track.

Install Shoverlay on the Mac App Store.