OBS Studio

Scene-based capture and streaming — the standard tool for recording a screen with overlays.

What it does

OBS composites sources (display capture, window capture, camera, microphone, browser page, image, text) into scenes, and either records them to disk or streams them over RTMP/SRT to any endpoint. Scene switching, per-source filters, audio mixing with per-track routing, and a virtual camera for use in other apps are all built in.

For documentation work the useful part is window capture plus a zoom/crop filter: a clean recording of one app at a fixed size, no desktop clutter.

Notes

Needs Screen Recording and Microphone permissions; macOS will silently record a black rectangle otherwise.
Hardware encoding uses VideoToolbox on Apple Silicon — much lighter than x264 for long recordings.
Plugins install to ~/Library/Application Support/obs-studio/plugins/.

Alternative to

Alternative	Type	Trade-off
ScreenFlow and Camtasia	Paid	Recording plus a real editing timeline
Ecamm Live	Freemium	Mac-native live production, much simpler than OBS
Streamlabs Desktop	Free	An OBS fork with streaming services bundled in
⇧⌘5 (Screenshot toolbar)	Built in	Built into macOS, enough for a plain screen recording
Loom	Freemium	Cloud, for recordings meant to be shared as links