A coded character scheme is a character encoding form plus byte serialization. It is a mapping of code units into serialized byte sequences. Whereas a character encoding form maps code points to code units, a character encoding scheme maps code units to bytes.

Character encoding schemes are required for cross-platform persistence involving code units wider than a byte. Most fixed-width byte-oriented encoding forms have a trivial mapping from code units to bytes. Most mixed-width byte-oriented encoding forms simply serialize the sequence of code units. Encoding forms with 16-bit or 32-bit code units require schemes that specify the byte order.

For example, the UTF-16 character encoding form for Unicode 3.0 has two character encoding schemes, UTF-16BE and UTF-16LE, which specify whether the two bytes used to represent UTF-16 code units are serialized in big-endian or little-endian format, respectively.