The journey of a URL
You type an address and press Enter. Half a second later, the page is there. This lesson takes that half-second apart: the full map of the journey.
The anatomy of a URL
Scheme, domain, port, path, query, fragment: read a URL piece by piece, and meet the part that never leaves your browser.
DNS, the web's address book
Machines speak IP, you speak names. DNS translates, in a cascade: cache, resolver, root, TLD. With a dig lab to read the address book yourself.
HTTPS: opening a secure channel
TCP picks up the phone, TLS encrypts the line. The handshake step by step, the certificate, and what the padlock really means (not that the site is honest).
Request, response, status codes
A raw request annotated line by line: methods, headers, and status codes. 2xx works, 3xx is elsewhere, 4xx is you, 5xx is the server.
Stateless, cookies and sessions
The server remembers nothing between two requests. So how does the site know you are logged in? The badge (cookie) and the locker (session), taken apart.
HTTP caching
Never re-download what has not changed: Cache-Control, ETag, and the 304 that answers without sending anything. The anti round-trip weapon.
CORS and HTTP/2, HTTP/3
Why the browser blocks your fetch to another API, and what HTTP/2 then HTTP/3 changed under the hood. End of the journey.
What you will learn
Follow the full journey of a URL: cache, DNS, TCP, TLS, request, response, render
Read a raw request and response: methods, headers, and the status code families
Understand stateless, cookies and caching: where things are stored, what travels, and why
Demystify HTTPS, the CORS error, and what HTTP/2 and HTTP/3 really change
Prerequisites: no networking background. The HTML basics help situate the examples. Every lab is simulated in the browser: dig terminal, curl requests, fake Network tab. Nothing to install.