In computing, an octet is a grouping of eight bits.

Octet, with the only exception noted below, always refers to an entity having exactly eight bits. As such, it is often used where the term byte might be ambiguous. For that reason, computer networking standards almost exclusively use octet. It is prominently used in Request for Comments (RFCs) published by the Internet Engineering Task Force. The earliest example is RFC 635 from 1974. In France, French Canada and Romania, the word octet is commonly used instead of byte (in the 8-bit sense); a megabyte (MB) is called a megaoctet (Mo).

Exception

The term "permission octet" is sometimes used for the group of basic permission bits (read, write, execute) of many file systems for Unix-like platforms. As these three bits can represent 8 different values octal notation is also used. The correct term "permission triplet" is also common though.

Normalization

Octets can be used with SI prefixes or the power of 2 prefixes as standardized by the International Electrotechnical Commission in 1998.

• kibi for « kilo binary » ;
• mebi for « mega binary » ;
• gibi for « giga binary » ;
• tebi for « tera binary » ;

The SI prefixes kilo, mega, giga, tera, etc., stay the same as for all the SI units, based on power of 10. In this case:

Origin

The word octet (meaning "group of eight") comes from the Latin and Greek numerical prefix octo, meaning eight.

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