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The `!octet`! is a `F33f`_`[unit of digital information`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Units_of_information]`_`f in `F33f`_`[computing`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Computing]`_`f and `F33f`_`[telecommunications`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Telecommunication]`_`f that consists of eight `F33f`_`[bits`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Bit]`_`f. The term is often used when the term `*`F33f`_`[byte`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Byte]`_`f`* might be `F33f`_`[ambiguous`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Ambiguity]`_`f, as the byte has historically been used for storage units of a variety of sizes.

The term `*octad(e)`* for eight bits is no longer common.`:cite-ref-philips-1971-1-0[`F5bf`_`[1`#cite-note-philips-1971-1]`_`f]`:cite-ref-williams-1969-2-0[`F5bf`_`[2`#cite-note-williams-1969-2]`_`f]

>>Contents

• `F0af`_`[Definition`#definition]`_`f

• `F0af`_`[Octad`#octad]`_`f

• `F0af`_`[Unit multiples`#unit-multiples]`_`f

• `F0af`_`[Use in Internet Protocol addresses`#use-in-internet-protocol-addresses]`_`f

• `F0af`_`[See also`#see-also]`_`f

• `F0af`_`[Notes`#notes]`_`f

• `F0af`_`[References`#references]`_`f

• `F0af`_`[External links`#external-links]`_`f

-─

>>Definition

The international standard `F33f`_`[IEC`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=International_Electrotechnical_Commission]`_`f 60027-2, chapter 3.8.2, states that a byte is an octet of bits. However, the unit `F33f`_`[byte`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Byte]`_`f has historically been `F33f`_`[platform`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Platform_(computing)]`_`f-dependent and has represented various storage sizes in the `F33f`_`[history of computing`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=History_of_computing]`_`f. Due to the influence of several major `F33f`_`[computer architectures`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Computer_architecture]`_`f and product lines, the byte became overwhelmingly associated with eight bits. This meaning of `*byte`* is codified in such standards as `F33f`_`[ISO/IEC 80000-13`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=ISO/IEC_80000-13]`_`f. While `*byte`* and `*octet`* are often used synonymously, those working with certain `F33f`_`[legacy systems`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Legacy_system]`_`f are careful to avoid ambiguity.

Octets can be represented using number systems of varying bases such as the `F33f`_`[hexadecimal`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Hexadecimal]`_`f, `F33f`_`[decimal`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Decimal]`_`f, or `F33f`_`[octal`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Octal]`_`f `F33f`_`[number systems`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Number_system]`_`f. The binary value of all eight bits set (or activated) is 111111112, equal to the hexadecimal value FF16, the decimal value 25510, and the octal value 3778. One octet can be used to represent decimal values ranging from 0 to 255.

The term `*octet`* (symbol: o`:cite-ref-nb-postfix-o-3-0[`F5bf`_`[nb 1`#cite-note-nb-postfix-o-3]`_`f]) is often used when the use of `*byte`* might be ambiguous. It is frequently used in the `F33f`_`[Request for Comments`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Request_for_Comments]`_`f (RFC) publications of the `F33f`_`[Internet Engineering Task Force`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Internet_Engineering_Task_Force]`_`f to describe storage sizes of `F33f`_`[network protocol`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Communication_protocol]`_`f parameters. The earliest example is `F33f`_`[RFC`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=RFC_(identifier)]`_`f 635 from 1974. In 2000, `F33f`_`[Bob Bemer`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Bob_Bemer]`_`f claimed to have earlier proposed the usage of the term octet for "8-bit bytes" when he headed software operations for `F33f`_`[Cie. Bull`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Cie._Bull]`_`f in France in 1965 to 1966.`:cite-ref-bemer-2000-4-0[`F5bf`_`[3`#cite-note-bemer-2000-4]`_`f]

In `F33f`_`[France`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=France]`_`f, `F33f`_`[French Canada`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=French_Canada]`_`f and `F33f`_`[Romania`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Romania]`_`f, `*octet`* is used in common language instead of `*byte`* when the eight-bit sense is required; for example, a megabyte (MB) is termed a megaoctet (Mo).

A variable-length sequence of octets, as in `F33f`_`[Abstract Syntax Notation One`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Abstract_Syntax_Notation_One]`_`f (ASN.1), is referred to as an octet string.

>>>Octad

Historically, in `F33f`_`[Western Europe`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Western_Europe]`_`f, the term `*octad`* (or `*octade`*) was used to specifically denote eight bits,`:cite-ref-williams-1969-2-1[`F5bf`_`[2`#cite-note-williams-1969-2]`_`f]`:cite-ref-philips-1971-1-1[`F5bf`_`[1`#cite-note-philips-1971-1]`_`f] a usage no longer common. Early examples of usage exist in British,`:cite-ref-williams-1969-2-2[`F5bf`_`[2`#cite-note-williams-1969-2]`_`f] Dutch and German sources of the 1960s and 1970s, and throughout the documentation of `F33f`_`[Philips`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Philips]`_`f `F33f`_`[mainframe computers`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Mainframe_computer]`_`f.`:cite-ref-philips-1971-1-2[`F5bf`_`[1`#cite-note-philips-1971-1]`_`f] Similar terms are `*triad`* for a grouping of three bits and `*decade`* for ten bits.

>>Unit multiples

Unit multiples of the octet may be formed with `F33f`_`[SI prefixes`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=SI_prefix]`_`f and `F33f`_`[binary prefixes`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Binary_prefix]`_`f (power of 2 prefixes) as standardized by the `F33f`_`[International Electrotechnical Commission`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=International_Electrotechnical_Commission]`_`f in 1998.

>>Use in Internet Protocol addresses

The octet is used in representations of `F33f`_`[Internet Protocol`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Internet_Protocol]`_`f `F33f`_`[computer network`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Computer_network]`_`f addresses.`:cite-ref-tcpip-5-0[`F5bf`_`[4`#cite-note-tcpip-5]`_`f] An `F33f`_`[IPv4`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IPv4]`_`f address consists of four octets, usually displayed individually as a series of decimal values ranging from 0 to 255, each separated by a dot (a `F33f`_`[full stop`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Full_stop]`_`f/period). Using octets with all eight bits set, the representation of the highest-numbered IPv4 address is `*255.255.255.255`*.

An `F33f`_`[IPv6 address`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IPv6_address]`_`f consists of sixteen octets, displayed in hexadecimal representation (two hexits per octet), using a colon character (:) after each pair of octets (16 bits are also known as `F33f`_`[hextet`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Hextet]`_`f) for readability, such as `*2001:0db8:0000:0000:0123:4567:89ab:cdef`*.`:cite-ref-rfc4291-6-0[`F5bf`_`[5`#cite-note-rfc4291-6]`_`f]

>>See also

• `F33f`_`[Variable-width encoding`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Variable-width_encoding]`_`f

>>Notes

`:cite-note-nb-postfix-o-3`!nb 1.`! `F0af`_`[↑`#cite-ref-nb-postfix-o-3-0]`_`f However, the `F33f`_`[IEC 80000-13`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IEC_80000-13]`_`f symbol "o" for octets can be confused with the postfix "o" to indicate `F33f`_`[octal numbers`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Octal_number]`_`f in `*`F33f`_`[Intel convention`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Intel_convention]`_`f`*.

>>References

`:cite-note-philips-1971-1`!1.`! `F0af`_`[↑`#cite-ref-philips-1971-1-0]`_`f "Philips - Philips Data Systems' product range - April 1971" (PDF). `F33f`_`[Philips`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Philips]`_`f. 1971. Archived from the original on 2016-03-04. Retrieved 2016-10-03.

`:cite-note-williams-1969-2`!2.`! `F0af`_`[↑`#cite-ref-williams-1969-2-0]`_`f `:citerefwilliams1969`aWilliams, R. H. (1969-01-01). `*British Commercial Computer Digest: Pergamon Computer Data Series`*. `F33f`_`[Pergamon Press`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Pergamon_Press]`_`f. `F33f`_`[ISBN`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=ISBN_(identifier)]`_`f 1483122107. 978-1483122106.

`:cite-note-bemer-2000-4`!3.`! `F0af`_`[↑`#cite-ref-bemer-2000-4-0]`_`f `:citerefbemer2000`a`F33f`_`[Bemer, Robert William`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Robert_William_Bemer]`_`f (2000-08-08). "Why is a byte 8 bits? Or is it?". `*Computer History Vignettes`*. Archived from the original on 2017-04-03. Retrieved 2017-05-15. […] I came to work for `F33f`_`[IBM`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IBM]`_`f, and saw all the confusion caused by the 64-character limitation. Especially when we started to think about word processing, which would require both upper and lower case. […] I even made a proposal (in view of `F33f`_`[STRETCH`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IBM_Stretch]`_`f, the very first computer I know of with an 8-bit byte) that would extend the number of `F33f`_`[punch card`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Punch_card]`_`f character codes to 256 […]. So some folks started thinking about 7-bit characters, but this was ridiculous. With IBM's STRETCH computer as background, handling 64-character words divisible into groups of 8 (I designed the character set for it, under the guidance of Dr. `F33f`_`[Werner Buchholz`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Werner_Buchholz]`_`f, the man who DID coin the term "`F33f`_`[byte`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Byte]`_`f" for an 8-bit grouping). […] It seemed reasonable to make a universal 8-bit character set, handling up to 256. In those days my mantra was "powers of 2 are magic". And so the group I headed developed and justified such a proposal […] The `F33f`_`[IBM 360`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=IBM_System_360]`_`f used 8-bit characters, although not ASCII directly. Thus Buchholz's "byte" caught on everywhere. I myself did not like the name for many reasons. The design had 8 bits moving around in parallel. But then came a new IBM part, with 9 bits for self-checking, both inside the CPU and in the `F33f`_`[tape drives`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Tape_drive]`_`f. I exposed this 9-bit byte to the press in 1973. But long before that, when I headed software operations for `F33f`_`[Cie. Bull`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Cie._Bull]`_`f in France in 1965-66, I insisted that "byte" be deprecated in favor of "octet". […]

`:cite-note-tcpip-5`!4.`! `F0af`_`[↑`#cite-ref-tcpip-5-0]`_`f `:citerefkozierok2005`aKozierok, Charles M. (2005-09-20) [2001]. "The TCP/IP Guide - Binary Information and Representation: Bits, Bytes, Nibbles, Octets and Characters - Byte versus Octet". 3.0. Archived from the original on 2017-04-03. Retrieved 2017-04-03.

`:cite-note-rfc4291-6`!5.`! `F0af`_`[↑`#cite-ref-rfc4291-6-0]`_`f `:citerefr-hindens-deering2006`aR. Hinden; `F33f`_`[S. Deering`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Steve_Deering]`_`f (February 2006). `*IP Version 6 Addressing Architecture`*. Network Working Group. `F33f`_`[doi`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Doi_(identifier)]`_`f:10.17487/RFC4291. `F33f`_`[RFC`:/page/wikibook/entry.mu`zim=wikipedia_en_all_nopic_2025-08.zim|entry_path=Request_for_Comments]`_`f 4291. `*Draft Standard.`* Obsoletes RFC 3513. Updated by RFC 5952, 6052, 7136, 7346, 7371 and 8064.

>>External links

• The dictionary definition of `*octet`* at Wiktionary

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