octets

An octet is a unit of digital information that consists of eight bits. In modern computing, octet is essentially equivalent to a byte, but the term is used deliberately to avoid ambiguity across architectures whose native byte size has varied. By international standards, an octet always represents eight bits, and a single octet can encode 256 distinct values (0 through 255) when interpreted as an unsigned value.

Historically, the size of a byte varied; the octet term arose to standardize eight bits as a basic building block. The octet is central in networking and information interchange, where protocol fields such as addresses, lengths, and payloads are expressed in octets to ensure portable definitions.

In practice, octets are used in IP networking; for example, an IPv4 address is four octets long, written as four numbers separated by periods. In data encoding, a character may occupy multiple octets (as in UTF-8), while legacy encodings may use a single octet per character. In many protocols, data lengths and identifiers are defined in octets to ensure interoperability.

The term is standard in telecommunications and standards bodies such as ISO/IEC and the IETF; it provides a fixed, architecture-agnostic unit that complements the broader concepts of bits and bytes. While the everyday term byte is common in software, octet remains the preferred unit in formal specifications.