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What is a Domain Name?

⏱ 6 min read

In one sentence: A domain name is a human-readable name, like wikipedia.org, that people use instead of a server's IP address.

Why should I care?

In IP Address, you saw that computers on the internet find each other with numbers called IP addresses. But you have probably never typed one. You type names like wikipedia.org or example.com. Those names are domain names.

A domain name is the name of a Server on the internet, such as the computer that sends you a website. At the end of this course, you can put your own website online with your own domain name.

Analogy

Think of the contacts on a phone. You do not remember your friend's phone number. You save it under a name, like "Ana", and you tap the name. The phone uses the number for you. If Ana gets a new number, you change the number, but you keep the name.

A domain name is like the contact name. The IP address is like the phone number.

Where the analogy breaks down: your contact names are private. Only your phone knows them, and you can choose any name you like. A domain name works for the whole world. Each one is unique, and you must register it before you can use it. And a domain name is only rented, for a limited time.

How it actually works

Why names instead of numbers

MDN, a website that explains how the web works, says: "IP addresses are hard to remember and might change over time." A domain name solves both problems. People remember the name. And if a website moves to a server with a new IP address, the name can stay the same.

To find the IP address that belongs to a name, your computer uses a system called DNS. You will learn how DNS does this in the next lesson.

The parts of a domain name

A domain name is made of parts called labels, separated by dots. You read it from right to left: from the biggest group to the smallest one. Each label to the left names a smaller part inside the domain to its right.

Diagram: the domain name en.wikipedia.org split into its three labels. Reading from right to left: "org" is the top-level domain. "wikipedia" and "org" together are the second-level domain wikipedia.org. "en" in front of it makes the subdomain en.wikipedia.org.

        en   .   wikipedia   .   org
        │         │              │
        │         │              └── org               top-level domain (TLD)
        │         └───────────────── wikipedia.org     second-level domain
        └─────────────────────────── en.wikipedia.org  subdomain

   read from right to left:  org  →  wikipedia.org  →  en.wikipedia.org
                           (biggest group)              (smallest part)
  • The last label, org, is the top-level domain, or TLD: the ending.
  • wikipedia.org is a second-level domain: one label in front of the TLD. This is usually the kind of name you register.
  • en.wikipedia.org is a subdomain: a smaller domain inside wikipedia.org. The owner of a domain can create subdomains, with different content at each. The www in www.example.com is a subdomain too.

Kinds of endings

There are two main kinds of top-level domains:

  • Country-code TLDs usually have two letters. Each one is for a country or territory (a place that is not a full country), like .id (Indonesia) or .jp (Japan).
  • Generic TLDs are the ones not made for one country. They usually have three or more letters, like .com and .org.

Some endings have strict rules about who may use them. For example, only "verified U.S. government organizations" can register a .gov name. Others, like .com and .org, have no such rules.

The rules for a name

MDN describes the rules for a label like this:

  • A label can use the letters A to Z, the digits 0 to 9, and the hyphen (-). A hyphen cannot be the first or last character.
  • Each label is 1 to 63 characters long.
  • Capital letters do not matter. WIKIPEDIA.ORG and wikipedia.org are the same name.

You can also have names in other alphabets, like Arabic or Chinese. Programs such as your browser turn these names into a form that uses only the letters, digits and hyphens above. Each converted label starts with xn--. This was first made a standard in 2003.

Who gives out domain names

  1. ICANN (the Internet Corporation for Assigned Names and Numbers) coordinates the whole system. It chooses the organizations that manage each TLD.
  2. Each TLD has a registry: a central list of all the names under that ending. For example, the .com registry is run by VeriSign Global Registry Services.
  3. You register a name through a registrar, a company that sells the right to use domain names. For generic endings like .com, registrars must be approved by ICANN. For a country ending, ICANN does not approve the registrars: the organization that runs the ending sets its own rules.

You cannot buy a domain name forever. The correct word is register, but it works like renting. MDN says: "you pay for the right to use a domain name for one or more years." You can renew it (pay again for more time), but "you never own the domain name." For endings like .com, ICANN's rules allow you to pay for at most ten years ahead.

How it came to be

You do not need to remember these names and dates. In October 1984, J. Postel and J. Reynolds published RFC 920. (An RFC is a public document that describes how a part of the internet works.) It listed the first top-level domains, including GOV (government), EDU (education), COM (commercial), MIL (military) and ORG (other organizations), and said countries would get two-letter codes. Many more endings have been added since then. The full list today is kept by IANA (the Internet Assigned Numbers Authority), which you met in IP Address.

🧪 Try it in your browser

You will look at the parts of domain names. These steps change nothing. Steps 1 to 3 also work on a phone.

  1. Click the address bar, type en.wikipedia.org and press Enter. What you should see: Wikipedia in English. The address may get longer, with the page's name after the domain name. That is normal.
  2. Now type de.wikipedia.org and press Enter. What you should see: Wikipedia in German. Both names end in wikipedia.org. Only the subdomain is different.
  3. Type EXAMPLE.COM in capital letters and press Enter. What you should see: a short page with the title "Example Domain", the same page you get with example.com. Capital letters do not matter.
  4. Type https://www.iana.org/domains/root/db/com.html in the address bar and press Enter. What you should see: a page with the heading .com. It says it is a "Generic top-level domain". It also names the organization that manages it.
  5. Now type https://www.iana.org/domains/root/db/jp.html and press Enter. What you should see: the page for .jp. This time it says "Country-code top-level domain".

Common misunderstandings

  • "I can buy a domain name and keep it forever." No. You pay to use it for one or more years, and you must renew it.
  • "Every website name starts with www." No. www is only a subdomain, and a website does not need it. en.wikipedia.org, for example, has no www.
  • "The ending tells you exactly who runs a website." Not always. MDN says the TLD is often only "a clue to the purpose, ownership, or nationality" of a website.

Recap

  • A domain name is a name for a server, used instead of its IP address. DNS finds the address that belongs to the name.
  • It is read from right to left: the TLD (like org), then the second-level domain (like wikipedia.org), then subdomains (like en.wikipedia.org).
  • You register a domain name through a registrar and pay to use it for one or more years; you never own it.

Sources

Written with AI · Reviewed by AI · Not yet checked by a human

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