What happens when you type a URL?
The most-asked tech interview question, animated. Five chapters take you from keystroke to pixels: DNS, TCP, TLS, HTTP, and Render. Pace it yourself — nothing autoplays.
Animated explanation of what happens when you type a URL into a browser — DNS resolution, TCP three-way handshake, TLS handshake, HTTP request and response, and browser render pipeline. Step-by-step interactive lesson built for IT students and engineers preparing for system design interviews.- ·What an IP address roughly is (a number that identifies a machine)
- ·Comfortable opening a browser and typing a URL
- ·Bonus: rough idea of what 'a server' is
Explain — to yourself, to an interviewer — every layer that runs between pressing Enter and the page appearing. Five chapters, pace yourself.
pace: 10 minutes total
Names get turned into IP addresses. The resolver does this for you in a single recursive query, but behind the scenes it walks the DNS tree from root → TLD → authoritative server.
Before anything moves — names vs IPs
You typed example.com and hit enter. But networks don't actually use names — they use IP addresses (like 93.184.216.34). DNS (Domain Name System) is the giant distributed phonebook that turns names into IPs. Your browser asks a helper called a 'resolver' to do that lookup.
DNS is hierarchical. Every dot in a domain name is a delegation boundary. example.com is delegated by .com which is delegated by the root.
keep going — these pair well with what you just learned.
OSI / TCP-IP layers
A packet wrapped layer-by-layer, then unwrapped on the other side. Watch headers stack and peel off — OSI 7 and TCP/IP 4 side by side.
DNS deep dive
Beyond the basics: recursive vs iterative, cache layers, TTLs, glue records, and what `dig +trace` actually shows.
NAT and routing
How packets cross networks. Source NAT, destination NAT, conntrack, routing tables — visualized with real IPs.