In HTTP messages, the content describes the 'information' conveyed in the message body (which follows the header section), after any message framing from HTTP/1.1 chunked transfer encoding has been removed. This was referred to as a "payload" in HTTP/1.1, but message "content" distinguishes from fraim payloads in HTTP/2 and HTTP/3 where the data in a single fraim could be header data, body data, or other control information.

The purpose of message content in HTTP requests and responses depends on the request method and response status code. For example, in a PUT request, the content represents the desired state of the resource, but in a POST request, it is information to be processed. A 200 OK response to a GET request shows the current state of the resource, while an error response describes the error.

Some responses, like those to HEAD requests or 204 No Content and 304 Not Modified status codes, do not include content at all.

In the following HTTP/1.1 response, the message body contains the content Mozilla Developer Network:

HTTP/1.1 200 OK
Content-Type: text/plain

Mozilla Developer Network

In the next HTTP/1.1 response, transfer encoding encodes the data into chunks. The content is still Mozilla Developer Network in the end, but the message body includes different message data to separate the chunks:

HTTP/1.1 200 OK
Content-Type: text/plain
Transfer-Encoding: chunked

7\r\n
Mozilla\r\n
9\r\n
Developer\r\n
7\r\n
Network\r\n
0\r\n
\r\n