What actually happens when you type a URL
By the end of today you can narrate the full path from pressing enter to seeing a page: name resolution, connection, request, response, and render, naming what could fail at each step.
YesterdayFor 22 days your programs ran alone on one machine. Today they start talking to other machines.
TomorrowTomorrow you go inside the request and response themselves, and learn what the parts mean.
Why this matters
This is the most asked interview question in the industry, and not because it is a trivia test. Every distributed system you meet later is a longer version of this same path.
- Client and server
- DNS
- TCP and TLS intuition
- The request lifecycle
Learn it
75 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
3 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
40 minUse dig or nslookup to resolve three domains and note the addresses. Then run curl -v against one of them and read the whole exchange out loud: what your machine sent, what came back, and which headers you can already explain. Finally, run curl against a domain that does not exist and describe exactly which step failed.
Recall it
25 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
5 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01A name becomes an address, an address plus port becomes a connection
- 02TLS costs round trips and buys confidentiality and identity
- 03The fragment never leaves the browser
- 04Each stage fails differently, and the symptoms look deceptively similar
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.