Editing UTF-7 (section)

==Byte order mark==
A byte order mark (BOM) is an optional special byte sequence at the very start of a stream or file that, without being data itself, indicates the encoding used for the data that follows; it can be used<!--it often isn't--> in the absence of metadata that denotes the encoding. For a given encoding scheme, it's that scheme's representation of Unicode code point <code>U+FEFF</code>.<ref>{{Cite web|url=https://unicode.org/faq/utf_bom.html|title=FAQ – UTF-8, UTF-16, UTF-32 & BOM}}</ref>

While it's typically a single, fixed byte sequence, in UTF-7 four variations may appear, because the last 2 bits of the 4th byte of the UTF-7 encoding of <code>U+FEFF</code> belong to the ''following'' character, resulting in 4 possible bit patterns and therefore 4 different possible bytes in the 4th position. See the UTF-7 entry in the [[Byte order mark#Byte order marks by encoding|table of Unicode byte order marks]].<ref>{{cite web| url=https://unicode.org/L2/L2021/21038-bom-guidance.pdf | title=Clarify guidance for use of a BOM as a UTF-8 encoding signature | access-date=2024-01-17}}</ref>