HTTP request

An HTTP request is a message asking a server to apply an HTTP request method to a target resource. It includes control information and HTTP header fields, and can include content according to the applicable method and message rules. Its meaning is distinct from the textual framing used by one protocol version.^[ref]

For an illustrative HTTP/1.1 request, the line GET /color?view=plain HTTP/1.1 selects a method and request target, while Host: example.org supplies host information. An empty line ends the header section. These pieces belong to the version's request-line and field syntax.^[ref]

Starting from https://example.org/color?view=plain#legend, the ordinary origin-form target is /color?view=plain. The query string participates in that target, while the fragment identifier does not: fragment processing is performed on the client side rather than by including the fragment in the target sent to the server.^[ref][ref]

The method cannot be inferred from a content string alone. Sending the text blue to an endpoint stipulated to replace a color and sending it to an endpoint stipulated to append a log entry request different operations. The target, method and application contract supply that distinction.

An HTTP request also differs from a returned HTTP response. A successfully transmitted request can receive an error status, and a connection can end before a final response is obtained. Reasoning about the requested operation, its eventual outcome and the transport event as separate observations makes failures easier to interpret.