{{Short description|Supplemental data placed after a block of data being transmitted}} {{Use American English|date = March 2019}} {{Use mdy dates|date = March 2019}}
In information technology, a '''trailer''' or '''footer''' refers to supplemental data (metadata) placed at the end of a block of data being stored or transmitted, which may contain information for the handling of the data block, or simply mark the block's end.<ref>{{cite journal|author1=Ambarisha Malladi|author2=M. Chandra Naik|author3=Sayyed Nagul Meera |title=Enhanced Packet Delivery Techniques Using Crypto-Logic on Jamming Attacks for Wireless Communication Medium|journal=International Journal of Computer & Organization Trends |year=2013 |volume=3 |issue=4 |page=109 |s2cid=18200687|url=https://pdfs.semanticscholar.org/d952/ce9228a9e8e898328867bc7c90eb4b085d44.pdf|archive-url=https://web.archive.org/web/20170309064912/https://pdfs.semanticscholar.org/d952/ce9228a9e8e898328867bc7c90eb4b085d44.pdf|url-status=dead|archive-date=2017-03-09|issn=2249-2593}}</ref>
In data transmission, the data following the end of the header and preceding the start of the trailer is called the payload or body.
It is vital that trailer composition follow a clear and unambiguous specification or format, to allow for parsing. If a trailer is not removed properly, or part of the payload is removed thinking it is a trailer, it can cause confusion.
The trailer contains information concerning the destination of a packet being sent over a network. So for instance, in the case of emails, the destination of the email is contained in the trailer.
==Examples== * In data transfer, the OSI model's data link layer adds a trailer at the end of frames of the data encapsulation.
==References== {{Reflist}}
Category:Computer data
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