UTF16UTF8

UTF16UTF8 is not an official Unicode encoding. The term is sometimes used informally to describe the process of converting text encoded in UTF-16 to UTF-8, or to systems that store text internally in UTF-16 and emit UTF-8. There is no standardized encoding by this name; instead, UTF-16 and UTF-8 are two distinct Unicode encodings with a defined relationship through transcoding.

UTF-16 encodes Unicode code points using 16-bit units. Code points in the Basic Multilingual Plane typically use one 16-bit unit, while supplementary characters are represented with a pair of 16-bit units known as surrogate pairs. UTF-16 can be stored in either big-endian or little-endian byte order, and many platforms may use a byte-order mark (BOM) to indicate endianness. Because of surrogate pairs, some characters require more than one 16-bit unit.

UTF-8 encodes code points as sequences of 1 to 4 bytes. It is byte-oriented, backward compatible with ASCII for the 0–127 range, and does not require a BOM. UTF-8 is widely used for data interchange and web content due to its ASCII compatibility and zero-surrogate complexity.

Transcoding between UTF-16 and UTF-8 is typically lossless when the source data is valid Unicode. Libraries perform decoding from UTF-16 (handling endianness and surrogates) and encoding into UTF-8. Potential pitfalls include invalid surrogate sequences, endianness mismatches, and improper handling of normalization or BOMs.