You press Enter

Alice types https://shop.example/cart and presses Enter. About a quarter of a second later her cart is on screen. In between, her browser talks to two other machines, trades about a dozen messages, and turns a stream of bytes into pixels.

This lesson slows that quarter second down about 25 times. Packets fly between the browser, a DNS resolver and the shop's server. Along the bottom, a waterfall records every phase in real milliseconds, the same view your browser's DevTools shows for any page.

Watch it once from end to end. Then we'll take it apart, one phase at a time.