Skip to lesson

How a page loadsPractice

Predict before you check.

Five questions. Commit to an answer, then read why each option is right or wrong.

Submodule 1 of 14Free interactive preview
Predict firstQuestion 1 of 5A newsletter links to https://shop.example, which answers with a redirect to https://www.shop.example. Nothing is cached. How many round trips pass before the first byte of the page?

Count one round trip for each DNS lookup, each handshake (TCP and TLS 1.3) and each request. The two names are on different servers.

Predict firstQuestion 2 of 5On a first visit, how many DNS lookups does this page need?

The page is on thinkfe.dev. It loads fonts from fonts.example.com and an analytics script from stats.example.net. Nothing is cached.

Predict firstQuestion 3 of 5A page has a deferred script, an async analytics script that takes 3 seconds to arrive, and a large photo that takes 5 seconds. Which is true?

Predict firstQuestion 4 of 5Two scripts: helpers.js defines a function that app.js calls. Which tags keep the page working and let parsing continue?

Predict firstQuestion 5 of 5Which requests delayed the first paint?

The head of index.html holds, in order: style.css; print.css, marked for printing only with its media attribute; app.js with no attribute; and main.js loaded as a module. The body has hero.jpg, and stats.js with async.

Tracks your place during this browser session. Sign in to save it to your account.

Next stepRecap

Keep the chain in your head.

Recall each idea before revealing it, then go to the sources.

Go to the recap