UTF-32

UTF-32 (or UCS-4) stands for Unicode Transformation Format 32 bits. It is a protocol to encode Unicode code points that uses exactly 32 bits per Unicode code point. This makes UTF-32 a fixed-length encoding, in contrast to all other Unicode transformation formats which are variable-length encodings. The UTF-32 form of a code point is a direct representation of that code point's numerical value.

The main advantage of UTF-32, versus variable-length encodings, is that the Unicode code points are directly indexable. Examining the n'th code point is a constant time operation. In contrast, a variable-length code requires sequential access to find the n'th code point. This makes UTF-32 a simple replacement in code that uses integers to index characters out of strings, as was commonly done for ASCII.

The main disadvantage of UTF-32 is that it is space inefficient, using four bytes per code point. Non-BMP characters are so rare in most texts, they may as well be considered non-existent for sizing issues, making UTF-32 up to twice the size of UTF-16 and up to four times the size of UTF-8.