Content header

Content headers are the group of HTTP headers that describe the content of the body of an HTTP message, after any message framing in the body has been removed. They specifically describe the properties of the message content that is conveyed in a particular message as it is transported, such as the length of the content, the transport encoding, which part of the resource is carried in the data (for multi-part messages), and message integrity checks. They differ from the Representation headers, which describe the encoding, media type, language, and other characteristics of the resource, and allow the underlying data to be interpreted.

These headers were defined as "Payload headers" in RFC 7231, but are now referred to as "Content headers" because data contained in HTTP/2 and HTTP/3 frame payloads could be header data, body data, or other control information. Later HTTP specifications don't mention "content headers" or expand on the list of relevant headers, but the semantics remain the same, so this way of classifying headers is still useful.

These headers may be present in both HTTP request and response messages and include:

• Content-Encoding
• Content-Length
• Content-Range
• Content-Type
• Trailer
• Transfer-Encoding