HalfBright mode is a screenmode of the Amiga micro computer. It uses 6 bitplanes (6 bits/pixel), where the first 5 bitplanes index a color from the color palette (consisting of 32 colors). If the bit on the 6th plane is set the color brightness is halved for each color component. This way 64 simultaneous colors are possible while using a 32 color palette.

The 32 colors per palette is a hardware limition for the pre AGA chipsets of the Amiga computer.

See also: HAM6