HTTP Request

A method, URL, headers and an optional body.

Backend Engineer · Junior Frontend Engineer · Junior Data Engineer · Junior

Also known as: HTTP request message, request line, request headers

An HTTP request is the message a client sends to a server. It has four parts.

POST /orders?source=web HTTP/1.1
Host: api.example.com
Content-Type: application/json
Authorization: Bearer eyJhbGciOi...
Accept: application/json

{"item_id": 7, "quantity": 2}

Part	Example	Meaning
Request line	`POST /orders?source=web HTTP/1.1`	the method, the path and query, and the protocol version
Headers	`Host`, `Content-Type`, `Authorization`	metadata about the request (headers)
Blank line		separates headers from the body
Body (optional)	`{"item_id": 7 ...}`	data being sent (body)

The full address comes from the Host header plus the path (and the scheme and port you connected with) (URLs).

What each part is for

Method: what to do (GET read, POST create…).
Path: which resource (/orders/917).
Query string: optional parameters, such as filters and paging (query strings).
Headers: who you are, what you send and accept, caching hints, cookies.
Body: the payload for POST, PUT and PATCH.

Seeing real requests

curl -v https://example.com          # shows the request it sends

The network tab in browser DevTools lists every request, with headers and bodies.

Points to remember

A GET normally has no body.
Header names are case-insensitive.
Cookies travel in the Cookie header.
Everything in a request is controlled by the client, so the server must validate it (never trust the client).
HTTP/2 and HTTP/3 carry the same information in a binary form.

The reply is an HTTP response.