What Is a Presentation Overlay?

A presentation overlay is the composite system that sits between the raw screen capture and the output video frame. It is a rendering layer that receives input from multiple sources — cursor position, keyboard events, user-triggered annotation tools, auto-zoom parameters — and composites corresponding visual elements (spotlights, keystroke badges, drawing strokes, dim overlays) on top of the screen content for each rendered frame. The key architectural property is non-destructive compositing: the overlay adds to the visual output without altering the application windows below it, meaning the presenter's apps continue to function normally throughout the recording.

The scope of a presentation overlay can range from minimal (just a cursor spotlight) to comprehensive (cursor spotlight, keystroke display, auto-zoom, region spotlight, freehand drawing, and click animations all active simultaneously). A well-architected overlay system ensures that these elements compose cleanly — drawing strokes appear above the spotlight, keystroke badges appear above the zoom transform, and cursor effects appear in the correct screen-space position after all other transforms are applied. The ordering and blending of overlay layers determines whether the final output looks clean and intentional or cluttered and confusing.

Limelight's presentation overlay is the underlying engine that coordinates all of its visual features. Cursor spotlight (⌃⌥1), keystroke display (⌃⌥2), freehand drawing (⌃⌥3), region spotlight (⌃⌥4), and on-screen text (⌃⌥5) are all managed by the overlay system, which applies each layer in the correct compositing order and synchronizes them with the auto-zoom transform before writing the final frame to disk. Because everything runs locally and offline, the overlay rendering has zero latency from network operations, and the exported video reflects exactly what was shown during the recording session — no cloud processing step required.