The RLE (Run Length Encoded) file format was the original format used by the Utah Raster Toolkit, an ensemble of graphics tools and C routines used for creating and manipulating complex compressed raster images.

RLE files were used in early versions of Windows and are essentially bitmap files compressed using Run Length encoding. The RLE format only supports 4, 8 or 16 bit color depths but requires minimal system resources for storage.

RLE files contain a header and the binary data responsible for displaying the image. The header of the file includes basic information about the raster image such as channels stored, comments and additional color maps.