Tech moves fast! Stay ahead of the curve with Techopedia!
Join nearly 200,000 subscribers who receive actionable tech insights from Techopedia.
A header is a part of a document or data packet that carries metadata or other information necessary for processing the main data. It is a widely used term in information technology that refers to any supplemental data that are placed before the actual data. The header usually marks the start of the data. When data are transmitted in datagrams, the header holds the important data such as the source and destination address, packet type and size, and related details. Similarly, the header is used in different types of documents for specific purposes.
A header is a part of a document, data packet or message that contains important information that is supplementary to the actual data. The contents of the header differ from document to document. Below are some examples of header contents:
Depending on the application, a header may be either optional (e.g., HTML document) or mandatory (e.g., data packet). It serves many purposes such as identification, authentication, verification, etc. The header of a data packet may also be used for tracing the path of the data packet from the sender to the receiver.