to UTF-8. UTF-16 is represented by 16-bit word arrays, and converting to UTF-16 while maintaining compatibility with existing ASCII-based programs (such as was done with Windows) requires every API and data structure that takes a string to be duplicated, one version accepting byte strings and another version accepting UTF-16. If backward compatibility is not needed, all string handling still must be modified. Text encoded in UTF-8 will be smaller than the same text encoded in UTF-16 if there are more code points below U+0080 than in the range U+0800..U+FFFF. This is true for all modern European languages. It is often true even for languages like Chinese, due to the large number of spaces, newlines, digits, and HTML markup in typical files. Most communication (e.g. HTML and IP) and storage (e.g. for Unix) was designed for a stream of bytes. A UTF-16 string must use a pair of bytes for each code unit: The order of those two bytes becomes an issue and must be specified in the UTF-16 protocol, such as with a byte order mark. If an odd number of bytes is missing from UTF-16, the whole rest of the string will be meaningless text. Any bytes missing from UTF-8 will still allow the text to be recovered accurately starting with the next character after the missing bytes. Derivatives The following implementations show slight differences from the UTF-8 specification. They are incompatible with the UTF-8 specification and may be rejected by conforming UTF-8 applications. CESU-8 Unicode Technical Report #26 assigns the name CESU-8 to a nonstandard variant of UTF-8, in which Unicode characters in supplementary planes are encoded using six bytes, rather than the four bytes required by UTF-8. CESU-8 encoding treats each half of a four-byte UTF-16 surrogate pair as a two-byte UCS-2 character, yielding two three-byte UTF-8 characters, which together represent the original supplementary character. Unicode characters within the Basic Multilingual Plane appear as they would normally in UTF-8. The Report was written to acknowledge and formalize the existence of data encoded as CESU-8, despite the Unicode Consortium discouraging its use, and notes that a possible intentional reason for CESU-8 encoding is preservation of UTF-16 binary collation. CESU-8 encoding can result from converting UTF-16 data with supplementary characters to UTF-8, using conversion methods that assume UCS-2 data, meaning they are unaware of four-byte UTF-16 supplementary characters. It is primarily an issue on operating systems which extensively use