Screen share
Share your screen (full screen, specific window or browser tab) live in a call. Standard since TeamViewer 2005; modern: Zoom, Teams, Meet, Discord, Slack Huddles. WebRTC under the hood.
Discord: screen share + voice-only "Stream mode" popular in gaming. Zoom: annotation overlay, dual-monitor support. Browser-tab-only sharing (Chromium feature) better for privacy — you don't accidentally share emails popping up. Remote control is a separate capability (TeamViewer, AnyDesk, Chrome Remote Desktop) — pair programming + IT support. Permission prompt on macOS/Wayland before the first share. Bandwidth: 720p screen ~1 Mbps, 1080p ~3 Mbps, 4K ~8 Mbps.