Header (computing)

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In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header is sometimes called the payload or body.

It is vital that header composition follows a clear and unambiguous specification or format, to allow for parsing.


  • E-mail header: The text (body) is preceded by header lines indicating sender, recipient, subject, sending time stamp, receiving time stamps of all intermediate and the final mail transfer agents, and much more.[1][2]

Similar headers are used in Usenet (NNTP) messages, and HTTP headers.

See alsoEdit


  1. ^ P. Resnick (ed.), Internet Message Format, Network Working Group, RFC 5322
  2. ^ B. Leiba, Update to Internet Message Format to Allow Group Syntax in the "From:" and "Sender:" Header Fields, Internet Engineering Task Force (IETF), ISSN 2070-1721, RFC 6854