The Unicode encoding scheme that serialises a UTF-16 code unit sequence as a byte sequence in either big-endian or little-endian format.

• In the UTF-16 encoding scheme, the UTF-16 code unit sequence <004D 0430 4E8C D800 DF02> is serialised as or or <00 4D 04 30 4E 8C D8 00 DF 02>.
• In the UTF-16 encoding scheme, an initial byte sequence corresponding to U+FEFF is interpreted as a byte order mark; it is used to distinguish between the two byte orders. An initial byte sequence indicates big-endian order, and an initial byte sequence indicates little-endian order. The BOM is not considered part of the content of the text.
• The UTF-16 encoding scheme may or may not begin with a BOM. However, when there is no BOM, and in the absence of a higher-level protocol, the byte order of the UTF-16 encoding scheme is big-endian.