bytelength

Bytelength is the number of bytes required to represent data in a given character encoding, typically for a string or other text payload. It is distinct from character length, which counts characters or code points rather than storage size. The bytelength of data depends on the encoding used and can vary even for strings that appear identical in a different context.

In ASCII, bytelength equals the number of characters since each ASCII character is encoded in one byte. In Unicode encodings, bytelength varies: UTF-8 uses 1 to 4 bytes per code point (for example, the letter “é” is two bytes, the euro sign “€” is three bytes, and the emoji “😀” is four bytes). UTF-16 uses 2-byte code units and may require four bytes for characters outside the Basic Multilingual Plane. UTF-32 uses a fixed four bytes per code point. The chosen encoding therefore directly affects bytelength.

Measuring bytelength is language- and encoding-specific. Python reports it as len(s.encode('utf-8')), or len(b) for bytes objects. Ruby provides string.bytesize. JavaScript in Node.js offers Buffer.byteLength(string, encoding) or, in modern environments, TextEncoder().encode(string). Java uses getBytes(encoding). C and C++ treat strings as sequences of bytes, with bytelength determined by the encoding and locale, and simple strlen counting bytes up to a null terminator rather than characters.

Applications include network transmission, file formats, database field limits, and user interfaces where storage or bandwidth quotas depend on the bytelength. When enforcing limits, truncation must respect encoding to avoid splitting multibyte characters and producing invalid output.