a variable-width encoding is a type of character encoding scheme in which codes of different lengths are used to encode a character set for representation in a computer. all of the common unicode encodings are variable-width encodings, e.g. utf-8 and utf-16. it's a common mistake to think that utf-16 isn't, so that's not a good reason to prefer utf-16 (only its obsolete predecessor ucs-2 is fixed-width).