Your phone has no idea where a website lives. Tap Go and watch it ask.

Before the envelope can travel, the internet looks the name up in its phone book (DNS) to get an address.

Tap the button, then tap each stop

What the internet can see

A sealed envelope. With HTTPS, the carriers move it but cannot read it. Without HTTPS, every one of them could.

Before any request left, the phone asked a directory: "what's the number for this name?" That directory is DNS, the Domain Name System.

Computers find each other by number. MDN: "An IP address is a number used to address each device on an IP network uniquely."

Humans are bad at numbers. As MDN puts it, "IP addresses are hard to remember and might change over time." So we use names.

Name in, number out
  1. You type a name

    shop.example.com

  2. The phone asks DNS

    "What number is this name?"

  3. DNS answers

    A number, the address of the right computer

  4. The request goes

    Straight to that number

The phone asks once, then remembers the answer for a while.

MDN calls DNS "a hierarchical and decentralized naming system". Think of it as a phone book spread across many computers, none of which holds the whole thing.

Answers get remembered for a while. That's why a change to a domain can take time to reach everyone: some phones still have the old number written down.

Try it with the rules off. In the sandbox, switch DNS off. The phone still knows the name, but it has no number to send the request to, so nothing leaves.

Check yourself

0/3 got it

Saved on this device only. No account, no streaks.

Next in the journey of a tap: What is a request?.