An alpha channel is an additional data channel in a video or image file that stores transparency information, allowing portions of the frame to be fully or partially transparent.
Standard video contains three channels of color data: red, green, and blue (RGB). An alpha channel adds a fourth channel that defines the opacity of each pixel, ranging from fully transparent to fully opaque, with every level of partial transparency in between. This enables video elements — like animated logos, lower thirds, visual effects, or isolated subjects — to be layered over other footage without a visible background.
Alpha channels are essential in compositing and motion graphics workflows. When a motion designer creates an animated title sequence, they export it with an alpha channel so the editor can place it over any footage without a colored background interfering. Similarly, green screen (chroma key) work ultimately produces footage with an alpha channel where the green background has been made transparent. Codecs that support alpha channels include ProRes 4444, DNxHR, VP9, and PNG sequences.
When requesting deliverables from a motion graphics artist or VFX team, specifying that files should include alpha channels ensures maximum flexibility in how those elements can be used. Assets with alpha channels can be composited over any background, resized, repositioned, and reused across multiple projects. They are particularly valuable as reusable brand assets — animated logos, lower thirds, and graphic elements that maintain their utility across many different videos.
Chroma keying is the compositing technique of removing a specific color (usually green or blue) from footage to create a transparent background, enabling replacement with any desired visual content.
Compositing is the process of combining visual elements from multiple sources — live-action footage, CGI, graphics, and effects — into a single, unified image that appears as though everything was captured together.
A matte is a mask or shape used to define which areas of a video frame are visible, hidden, or partially transparent, enabling selective compositing and effects application.