Alpha channel

An alpha channel is the extra channel in an image or video that stores how transparent each pixel is, next to the red, green and blue color channels. A pixel with full alpha is solid, a pixel with zero alpha is invisible, and the values in between are partly see-through, which is how soft edges and glows blend over what is behind them.

In video, the alpha channel is what makes a transparent overlay possible: captions, a lower third, an arrow or a sticker rendered on its own, without a background, so you can lay it on top of any clip in an editor.

Formats that keep transparency

When the editor ignores alpha

Some apps, including CapCut and many phone editors, ignore the alpha channel of imported video and show black instead. The fallback is a green-screen version: the overlay rendered on a solid green background, which the editor removes with its chroma key tool. Designs meant for keying avoid soft green-tinted glows, because those do not key cleanly.

Rendering transparent video with code

In HyperFrames, a transparent render needs a transparent page: no background color on the page or the root element in that version, then --format webm or --format mov. Check the result over a contrasting background; some players always show black behind alpha even when it is there.

In Motion Cheat Code

The 60 overlays in the pack come three ways: a transparent WebM, a green-screen MP4 and the HyperFrames source, so they work in any editor and can be recolored with a prompt. Several templates, including Lower Third, Karaoke Captions, Keyword Pop and Stat Sticker, are built to render transparent.