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What are HTTP messages?

HTTP messages are how data is exchanged between a server and a client.

There are two types of HTTP messages:

  • HTTP requests, sent by the client to trigger an action on the server.

  • HTTP responses, the answer from the server.

Clients and servers communicate by exchanging individual messages (as opposed to a stream of data). The messages are human-readable.

Structure of requests and responses

HTTP message structure

Source: MDN Web Docs

HTTP requests and responses share a similar structure and include:

  1. a start-line that describes the request being made, or its success status. Always a single line.

  2. optional HTTP headers for specifying the request or describing the body included in the message.

    Header fields are key-value pairs separated by colons.

  3. a blank line indicating all meta-information for the request has been sent.

  4. an optional body that contains data associated with the request or the document associated with the response.

HTTP Request

HTTP request

Source: MDN Web Docs

HTTP Method

Defines the operation the client wants to perform. Options include:

  • GET
  • POST
  • PUT
  • DELETE

Path

The path of the requested resource.

Version

Version of HTTP protocol

Headers

Optional headers to convey additional information for the servers

Body

A POST method would contain the resource being sent to the server.

HTTP Response

HTTP response

Source: MDN Web Docs

Version

Version of HTTP protocol

Status code

Indicates whether a specific HTTP request has been successfully completed.

Status message

A non-authoritative short description of the status code.

Headers

HTTP headers, like those for requests.

Header fields are key-value pairs separated by colons.

Body

Optional. Contains the fetched resource.

Sources