How the Internet Works

What happens between typing a URL and seeing the page.

When you load a web page, your request is split into packets, passed between many machines and put back together at the other end. This track walks through each step: DNS, TCP/IP, HTTP, TLS and what the browser does with the response.

  • Beginner
  • 7 lessons
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Lessons

  1. The Big Picture: Packets & LayersThe internet splits every message into small packets, sends each one separately and reassembles them at the other end. This lesson explains packets and the layers that carry them.
  2. IP Addresses & RoutingEvery machine on the internet has an address. You'll learn how IP addresses, NAT and routing let your laptop reach a server on the other side of the world.
  3. DNS — The Internet's Phone BookDNS translates names like example.com into IP addresses like 93.184.216.34. It's the first step of every page load, and you'll learn how a lookup works and how to inspect one.
  4. TCP & UDP — Reliable vs FastIP can lose, duplicate or reorder packets. TCP adds reliable, ordered delivery on top, while UDP skips those guarantees for speed, and you'll learn when each is used.
  5. HTTP & HTTPSHTTP is a simple text conversation of requests and responses, and HTTPS wraps it in TLS encryption. You'll learn methods, status codes, headers and what the padlock actually means.
  6. The Full Journey: URL to PixelsThis lesson puts the track together, following a page load from DNS lookup to rendered page. It also covers how the browser turns HTML and CSS into pixels.
  7. Internet CheatsheetLayers, ports, status codes, and debug commands — one page.

Install it on your own computer

This is a concepts track, so there is nothing to install. These built-in tools let you see each layer at work, and each lesson uses one or two of them.

Bash
# All built in (PowerShell):
nslookup example.com        # DNS lookups
ping example.com            # reachability + latency
tracert example.com         # the route your packets take
curl.exe -v https://example.com   # raw HTTP conversation

What people build with How the Internet Works

Learn the basics first, then pick up these tools when a project needs them.

Practical uses

  • Debug requests across browsers, servers, and networks
  • Design reliable HTTP APIs
  • Understand DNS, TLS, caching, and CDNs
  • Secure and operate internet-facing systems

Projects to try

  1. HTTP request inspector
  2. DNS lookup visualizer
  3. Tiny HTTP server
  4. Caching reverse proxy

Common tools and packages

curlWiresharkdigPostmanmitmproxyngrokCloudflareOpenSSL

Well-known software

NginxApache HTTP ServerBINDCloudflare CDNChrome DevToolsLet’s Encrypt