In its first versions, the CDR file format was a completely proprietary file format primarily used for vector graphic drawings and developed by Corel Corporation, recognizable by the first two bytes of the file being "WL". Starting with Corel Draw 3, the file format changed to a Resource Interchange File Format (RIFF) envelope, recognizable by the first four bytes of the file being "RIFF", and a "CDR*vrsn" in bytes 9 to 15, with the asterisk "*" being in early versions just a blank, and beginning with Corel Draw 4, the version number of the writing program in hexadecimal ("4" meaning version 4, "D" meaning version 14). The actual data chunk of the RIFF remains a Corel proprietary format.
Portable Network Graphics (PNG), is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format (GIF), and is the most used lossless image compression format on the Internet. PNG supports palette-based images (with palettes of 24-bit RGB or 32-bitRGBA colors), grayscale images (with or without alpha channel), and full-color non-palette-based RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet, not for professional-quality print graphics, and therefore does not support non-RGB color spaces such as CMYK.