The Request: Method, Headers, Body

When the Tandem app checks how many bikes are at Old Market, something leaves the phone. It is worth pausing on what that something actually is — because most people imagine streams of machine code, unreadable by design. The truth is better: what leaves is a short piece of plain text called a request, a handful of lines long, and you can read every character of it.

Seeing that — that the whole mysterious exchange is a few lines of readable text — is where the fear starts dying. This page shows a complete request and names its three parts: the request line, the headers, and the body. Every request you will ever send or see has exactly this shape.

GET /v1/stations/st_014 HTTP/1.1
Host: api.tandem.example
Accept: application/json
User-Agent: TandemApp/4.2

Four lines of text. That is the entire request the app sends to ask about Old Market. Now, part by part.

The Request Line: What You Want, and Where

The first line does the heavy lifting: GET /v1/stations/st_014 HTTP/1.1. Three pieces. The method — here GET — is the verb, what kind of act this is; GET means "give me this, change nothing," and the verbs get their own page two topics from now. Then the path — the room, straight from the last page. Then the HTTP version the sender speaks. One line, and the server already knows what is being asked of it.

Headers: Notes on the Envelope

The lines after the request line are headers — one per line, each in the form Name: value. Think of them as handling notes written on the outside of an envelope: who is sending this, what form of answer they can accept, how the contents are packed. In the example: Host names the building (the URL's host, restated inside the request), Accept says "I would like the answer as JSON, please" — JSON being the data format Chapter 4 teaches — and User-Agent is the sender introducing itself.

Most headers are optional — Host is the required exception — but one of them will shortly become the difference between locked out and let in: from Chapter 5 on, your key travels in a header called Authorization, on every single request. Headers are where the important envelope-notes go, and the habit of reading them starts now.

The Body: the Parcel, When There Is One

Notice what the example does not have: a body. A body is content carried inside the request — an actual parcel, not just notes on the envelope. A GET carries none, because "give me this" needs no cargo; the ask is the label. Requests that send something in — creating a reservation, submitting a form — carry their cargo in the body, usually as JSON, with a header called Content-Type announcing the format. You will send your first body in Chapter 3, and it will feel exactly like what it is: filling in one small form.

Read One Whole Request

Go back to the four lines above and read them once more, slowly. A verb, a room, a dialect. A building name. A preference. A signature. Nothing hidden, nothing binary, nothing you could not have typed yourself. When something goes wrong in Chapter 7 and a support engineer asks Vera "what did you send?", this page is what makes that question answerable — because a request is not an event that happens to you. It is a document you can show.