Header (computing)

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 also


  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
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