HTTP, Explained

Every time you open a website, two computers have a short, polite conversation. Your browser asks for something; a server hands it back. That conversation is HTTP - the language the web speaks. You've relied on it every day of your life online without ever being shown how it works, and that's fine, until the day a page returns 404, or a developer mentions a "POST request," or you see https:// turn red and wonder if you're about to be robbed.

This guide is the manual nobody handed you. By the end you'll be able to picture exactly what your browser and a server are saying to each other, read a status code without panic, and understand what that little padlock in the address bar is actually protecting. No deep networking background needed - we start from the conversation and build up.

How to read this

• Want a specific answer right now? Phase 2 has the status-code table - if you just want to know what 404 or 500 means, jump to Phase 2: Methods & Status Codes.
• Want it to finally make sense? Read in order. Each phase builds on the last: the conversation first, then the words it uses, then the details that ride along.

The phases

1. Request & Response - the core model: your browser sends a request, the server sends a response. Plus the anatomy of a URL, the address you're really typing.
2. Methods & Status Codes - the verbs (GET, POST, PUT, DELETE) and the three-digit replies (2xx, 3xx, 4xx, 5xx), with a table and how to read a code calmly.
3. Headers, Cookies & the S in HTTPS - the extra notes each message carries, how sites remember you, and what encryption actually buys you.

This guide stops at the everyday mental model. The deeper machinery - how packets actually travel, ports, DNS, and the layers underneath HTTP - lives in its own guides: How the Internet Works, IP, DNS, and Ports, and The TCP/IP Model. APIs are built directly on top of HTTP, so a future guide on what an API is will link back here.