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Domain name

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A domain name is a text label used on the Internet.

An annotated example of a domain name
An annotated example of a domain name

Computers use numbers called IP addresses to find each other. These numbers can be very hard for people to remember. Domain names solve this problem by using easy words instead. A domain name can identify a whole network or just one computer. These computers are often called hostnames. Using names makes it much easier to reach websites or email services.

DNS schema
DNS schema

Domain names work through a system called the Domain Name System, or DNS. This system is organized like a tree with many branches. The tree starts at a nameless root at the very top. From the root, the first level of names is called a top-level domain, or TLD. Some TLDs are generic, like .com, .net, or .org. Others are country code TLDs that use two letters.

Domain name space
Domain name space

Below these are second-level and third-level domains. These are often the names people choose for their own websites.

In the early days of computer networks, things worked differently. People used a system called ARPANET before the modern Internet existed. Each computer had to get a file called host.txt from a computer at SRI. This file matched names to the correct numbers. As the network grew, this central list became too hard to manage. Because of this, the Domain Name System was introduced in 1983. It was published by the Internet Engineering Task Force.

DNS schema
DNS schema

Domain names are made of parts called labels. These labels are separated by dots. For example, in www.example.com, the right-most label is the TLD. The labels to the left are called subdomains. A fully qualified domain name, or FQDN, includes every label in the hierarchy. These names can be up to 253 characters long. Each individual label can be between 1 and 63 characters. Most people write domain names in lowercase letters.

An annotated example of a domain name
An annotated example of a domain name

Today, a group called ICANN manages the top levels of the Internet. They authorize registrars to sell names to the public. When you use a registrar, you get the right to use a name for a set time. This is not the same as legal ownership. Domain names help us connect to things we already know. You might see a name like books.com or travel.info. These names help people find specific types of services very quickly.

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File:An annotated example of a domain name.png
An annotated example of a domain name.png
File:Domain name space.svg
Domain name space.svg
File:DNS schema.svg
DNS schema.svg
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