How the Internet Works
What really happens between your tap and the page, in moving pictures you step through one frame at a time.
For anyone who uses the internet all day and has never been shown what is under it. No maths, no code. You follow one request from your phone to a server and back, and every lesson has an animated diagram you step through: addresses, packets, DNS, routers, the handshake, the padlock, caches, the cables under the sea. You finish able to explain why a page is slow, what the padlock does and does not protect, and how to spot a fake address before you type a password into it.
By the end you can
- Follow one request from your phone to a server and back, naming what happens at each step
- Explain what DNS, IP addresses, packets and routers each do, using a real example
- Say what the padlock in the address bar protects, what it doesn't, and spot a look-alike address
- Diagnose a slow connection: tell latency from bandwidth and know which one a fix would change
From your tap to a server
- What happens when you open a website
Follow the whole trip from typing a web address to seeing the page on screen, and meet the five words — server, IP address, DNS, request, packet — the rest of this course builds on.
- Addresses: how a device is found
See why the address your phone shows at home (192.168.1.x) isn't what the internet actually sees, meet the router's public address (203.0.113.5), and learn how NAT gets a reply back to the right device.
- Packets: chopping a message into pieces
See why every message on the internet travels as small numbered packets instead of one lump, how they can arrive out of order and get reassembled, and why that design survives a lost piece so cheaply.
Names, routes and reliable delivery
- DNS: the internet's phone book
DNS turns the name you typed into the address a machine actually needs, in a few quick asks you never see. Learn why that answer gets remembered for a while, and what it usually means when a site won't load for you but loads fine for a friend.
- Routers: finding a path, and another one
A router only knows its own neighbours, not the whole internet, yet your packets still cross the world and find their way around a broken link. See what a hop is, why no single map of the internet exists, and why a site down the street can still take the long way round.
- TCP: making sure everything arrives
Packets can be lost, duplicated or arrive out of order, so TCP adds a conversation on top: a handshake to open the line, a number on every piece, and a resend whenever an acknowledgement doesn't show up. See where that's worth the wait, and where a call or a game skips it on purpose.
The web itself
- HTTP: asking for a page and getting an answer
See the exact text message your phone sends when it asks for a page, and read a server's answer well enough to know whether a broken page is on you or on it.
- HTTPS: what the padlock protects
See why anyone sharing your Wi-Fi can read a plain HTTP page, how TLS locks the connection so only the two ends can read it, and what the padlock does and doesn't promise before you ever type a password.
- Caches and CDNs: why the second visit is fast
See why a page loads slow the first time and fast right after, what your browser's cache and a CDN each keep close to you, and why a hard refresh is sometimes the fix for a stuck old page.
The bigger picture
- Wi-Fi, cables and the sea floor
See the real, physical path your data takes: a few metres of radio, then cable and fibre the rest of the way, some of it laid across the sea floor. You'll be able to explain why "the cloud" is just a building, and what happens when a cable gets cut.
- Why it feels slow: latency and bandwidth
Tell apart the two very different reasons a connection feels slow: how much data arrives per second, and how long one round trip takes. You'll be able to read a speed test and know which fix actually helps.
- Staying safe: look-alike sites and second steps
Turn everything from this course into one habit: read an address bar in three seconds, spot the pattern of a rushed login, and know which two habits catch what your eye misses.
Keep it, don't just read it
Pathwise brings each idea back just before you'd forget it, with a quick question. Free on Android and on the web, in English and Persian.