Files with the .BMP extension contain an uncompressed raster image, or an image subjected to a non-lossy RLE compression. The data is saved in the form of a heading that defines the color scale and the height and width of the image in pixels, which is followed by data concerning the colors of each individual pixel, from the bottom upwards.

The color scale defined in the heading depends on the number of bits dedicated to storing information about each pixel, and it can also be a greyscale. The information contained in the file can also be expanded, for example by a path to an ICC color profile.