utf

UTF stands for Unicode Transformation Format, a family of encodings for Unicode code points. It translates the characters defined by the Unicode standard into sequences of bytes for storage, transmission, and processing. The most widely used forms are UTF-8, UTF-16, and UTF-32. All three are designed to represent the full range of Unicode code points, up to U+10FFFF, and to interoperate with existing text-processing systems.

UTF-8 is a variable-length encoding that uses one to four bytes per code point. Code points in the ASCII range (U+0000 to U+007F) are encoded as a single byte identical to ASCII. Other code points use multi-byte sequences with distinct leading-bit patterns. UTF-8 is backward compatible with ASCII, does not require a byte order mark for binary data, and is the dominant encoding for web content and most modern data formats.

UTF-16 uses 16-bit code units. Code points in the Basic Multilingual Plane (U+0000 to U+FFFF) fit in one unit; code points above U+FFFF are encoded using a pair of 16-bit units called surrogates. UTF-16 can be encoded in little-endian or big-endian byte order and may use a byte order mark to indicate endianness. It is commonly used in Windows and in some programming environments such as Java.

UTF-32 uses fixed 32-bit code units, with each Unicode code point mapped directly to a single 4-byte value. This makes random access simple but results in larger file sizes, so UTF-32 is less common for general text storage. It is used in some internal applications where simple indexing is important.

Endianness, normalization, and compatibility considerations influence how UTF forms are implemented in software and protocols. UTF encodings are standardized as part of the Unicode specification and related ISO/IEC 10646 standards, and are used to exchange most global text across networks, filesystems, and programming languages.