What Is DNS?
What the Domain Name System does
What is DNS? DNS, short for Domain Name System, is the internet's naming directory. It translates a domain name such as example.com into the numeric IP address, for example 192.0.2.10, that computers use to reach each other. Without DNS, visitors would have to memorize a number for every website they wanted to open.
Network equipment routes data by IP address, but people remember names. DNS fills that gap. When you enter a web address in your browser, a DNS lookup runs in the background to find the server that hosts the site. Most of the time you never notice it, and when the answer is already stored nearby, it takes only a few milliseconds.
DNS does far more than load web pages. The same system tells mail servers where to deliver email for a domain, lets services check that you control a domain, and points applications such as chat and voice tools to the right servers. For the step-by-step process, read how a DNS lookup works from start to finish.
The building blocks: names, records and servers
DNS rests on three main parts. The first is the namespace, a tree of names read from right to left. At the top are top-level domains such as .com, below them sit domains such as example.com, and below those come subdomains such as shop.example.com.
The second part is the records. A record is a small piece of data attached to a name. Examples include an IPv4 address (an A record), a mail server (an MX record) and a text value used for verification (a TXT record). A single name can hold several records of different types, as explained in the common DNS record types.
The third part is the servers that store and answer these records. Each zone, the part of the namespace managed by one administrator, is held on authoritative nameservers. Separate recursive resolvers ask questions on behalf of users. Because responsibility is split among many servers, DNS scales to the size of the internet and keeps working when one server fails.
Example: moving a website to a new host
A small business moves its website to a new hosting provider. The new server is set up and the site files are uploaded, but visitors still see the old site. The reason is DNS. The domain's records still point to the IP address of the old server.
The business updates the A record for its domain to the address of the new server. From then on, a new lookup returns the new address. Resolvers that stored the old answer keep using it until its time to live (TTL) runs out. TTL is the setting that controls how long a DNS answer may be cached. For a while, some visitors reach the old server and others reach the new one.
Frequently asked questions
Is DNS the same thing as a domain name?
No. A domain name is the human-friendly address you register, such as example.com. DNS is the system that stores and answers questions about that name, returning the IP addresses and other records linked to it. A domain name needs DNS to work on the internet, but DNS itself is the infrastructure behind it.
Who runs the Domain Name System?
No single company runs DNS. The root zone is coordinated by ICANN, the root servers are operated by several independent organizations, and each top-level domain is managed by its registry. Individual domains are run by their owners or by the DNS providers they choose. This shared responsibility is what lets DNS work across the whole world.