Who is FEFF?
The byte-order mark (BOM) is a particular usage of the special Unicode character code, U+FEFF ZERO WIDTH NO-BREAK SPACE, whose appearance as a magic number at the start of a text stream can signal several things to a program reading the text: the byte order, or endianness, of the text stream in the cases of 16-bit and 32-bit encodings; the fact that the text stream's encoding is Unicode, to a high level of confidence; which Unicode character encoding is used. BOM use is optional. Its presence interferes with the use of UTF-8 by software that does not expect non-ASCII bytes at the start of a file but that could otherwise handle the text stream. Unicode can be encoded in units of 8-bit, 16-bit, or 32-bit integers. For the 16- and 32-bit representations, a computer receiving text from arbitrary sources needs to know which byte order the integers are encoded in. The BOM is encoded in the same scheme as the rest of the document and becomes a noncharacter Unicode code point if its bytes ar...
