A digital image format that extends 24-bit colour by adding an alpha channel for transparency. Each pixel contains 8 bits each for red, green, and blue channels, allowing 16.7 million colours, plus 8 bits for the alpha channel, providing 256 levels of opacity. This makes 32-bit images ideal for compositing, overlays, and graphics requiring transparency or semi-transparent effects, commonly used in digital imaging, video, and web design.