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From Enter to 200 OK: Anatomy of a Web Request

Follow a web request from pressing Enter to rendered pixels, exploring DNS, routing, TCP, TLS, HTTP, browser security, infrastructure, backend systems, and observability.

  • networking
  • web
  • backend
  • security

In this series we’ll go follow the journey of a web request from the moment you press Enter to the moment the response becomes pixels on your screen.

Along the way, we’ll look at each layer involved: what problem it solves, what information it receives and passes forward, what usually remains hidden from application developers, and how things can fail. We’ll also use practical demonstrations to inspect these layers and explore the security implications at each stage.

At a high level, this is what the path we’ll follow through the series:

Press EnterBrowserDNSRoutingTCP / QUICTLSRenderingHTTP ResponseApplicationEdge & InfrastructureBrowser SecurityHTTP

We’ll break this journey into 10 articles:

  1. You Pressed Enter. Now What?
  2. DNS: How Do We Find the Server?
  3. We Have an IP Address. How Do We Reach It?
  4. TCP, Sockets, and Connections
  5. TLS and HTTPS: Can We Trust This Server?
  6. Finally, HTTP
  7. Cookies, CORS, and Browser Security
  8. Your Request Probably Never Reached the Application Directly
  9. Now Your Application Runs
  10. The Response Comes Back: From HTTP to Pixels

Most of this happens in milliseconds and is usually hidden behind browsers, operating systems, frameworks, and cloud infrastructure. Over the next ten articles, we’ll unpack those abstractions one layer at a time.