Free course · 6 lessons · 20–30 min
How the internet actually works
Follow one web page from your screen to a server and back.
What you’ll learn
Explain what happens between tapping a link and seeing the page, and name the part to blame when something goes wrong.
Before you start
You use the internet every day. No networking or programming knowledge is required.
Course outline
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Chapter 1
The journey of a page
Follow one page load from start to finish, then see why data travels in small pieces and how those pieces find their way.
- What happens when you open a pageThe whole trip from your screen to a server and back, in five steps.3 min
- Why everything travels in packetsSee why the internet chops every message into small numbered pieces, and what happens when one goes missing.3 min
- How packets find their wayIP addresses, routers that only know the next step, how networks share directions, and the cables on the seabed.3 min
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Chapter 2
Names, lost packets, and trust
Turn names into addresses, recover what the network loses, and find out what the padlock really guarantees.
- DNS, the internet's phone bookHow a name like wikipedia.org turns into an address, and why that usually takes milliseconds.3 min
- TCP, UDP, and lost packetsTwo ways to handle a network that loses things: resend everything, or keep moving.3 min
- What the padlock promisesWhat HTTPS protects, how your phone knows it reached the real site, and what the padlock can't tell you.3 min