MIME type: image/bmp BMP Windows bitmap format. Raster image format. Native bitmap format of the Microsoft Windows operating system. BMP is an acronym derived from Bitmap. Binary file format. Stores color bitmaps at a variety of color resolutions. Allows different bit depths in different channels. Has support for color reduction palettes using up to 256 8-bit RGB colors. Supports transparency. Stores data in uncompressed or run-length encoded form.