Headerdaten

Headerdaten, or header data, are metadata fields that accompany a data unit in computing and communications. They appear at the beginning or as part of the data packet and describe the content and how the rest of the data should be interpreted or routed. Header data is distinct from payload, which is the actual content.

Header data are used in various domains, including network protocols, file formats, and data storage. Typical fields include version or type, length or size, timestamp, source and destination identifiers, and a checksum or integrity check. The exact fields and their encoding depend on the protocol or format.

In network communications, headers enable routing, sequencing, and error detection. For example, IP headers carry version, header length, total length, and addresses; TCP headers add ports, sequence numbers, acknowledgment numbers, and flags.

In the context of the World Wide Web, headers in HTTP requests and responses convey metadata such as Host, User-Agent, Content-Type, and Content-Length, guiding how the body is processed.

In file formats, headers may specify format details like image dimensions, color depth, or compression method; in emails, header lines include From, To, Subject, and Date.

Header data can be fixed-length or contain variable-length fields. They are essential for parsing, validation, and interoperability but can also carry privacy or security considerations, as headers may expose information even when the payload is encrypted.