What is the Domain Name System (DNS)?

Every time you visit a website, you are interacting with the largest distributed database in the world. This massive database is collectively known as the DNS, or the Domain Name System. Without it, the Internet as we know it would be unable to function. The work that the DNS does happens so seamlessly and instantaneously that you are usually completely unaware that it's even happening. The only time that you'll get an inkling about what the DNS is doing is when you're presented with an error after trying to visit a website. Learn more about what the DNS is, how it works and why it's so critical by reading on below.

IP Addresses and Domain Names

In order to understand what the DNS is and how it works, you need to have a basic understanding of IP addresses and domain names. An IP address, or Internet Protocol address, is a complex string of numbers that acts as a binary identifier for devices across the Internet. In short, an IP address is the address that computers, servers and other devices use to identify one another online. The vast majority of IP addresses are arranged into four sets of digits – i.e.,

A domain name is the information that you enter into a web browser in order to reach a specific website. When you input a URL like www.example.com/index into a web browser, its domain name is example.com. Basically, a domain name is the human-friendly version of an IP address. Businesses vie for easy-to-remember domain names, since they make it easier for people to remember how to find them online. If people had to remember complex IP addresses in order to navigate the Internet, it wouldn't be nearly as useful or enjoyable.

Translating Domain Names into IP Addresses

Although it's possible to enter an IP address into a web browser into order to get to a website, it's a lot easier to enter its domain name instead. However, computers, servers and other devices are unable to make heads or tails of domain names – they strictly rely on binary identifiers. The DNS's job, then, is to take domain names and translate them into the IP addresses that allow machines to communicate with one another. Every domain name has at least one IP address associated with it.

Top Level Domains, Root Servers and Resolvers

The DNS is a remarkable database. It doesn't perform its work alone, though. Things called Top Level Domains (TLDs) and root servers do a lot of the heavy lifting for the DNS. A Top Level Domain refers to the part of a domain name that comes after the period. For instance, the TLD of example.com is COM. While there's an ever-expanding number of domain names, there's a relatively static number of Top Level Domains; .com, .edu and .org are just a few key examples.

Specialized computers called root servers store the IP addresses of each Top Level Domain's registries. Therefore, the first stop that the DNS makes when it resolves, or translates, a domain name is at its associated root server. From there, the requested domain name is sent along to a Domain Name Resolver, or DNR. Domain Name Resolvers, or resolvers, are located within individual Internet Service Providers and organizations. They respond to requests from root servers to find the necessary IP addresses. Since the root server already recognizes the .com, .edu or other part of the equation, it simply has to resolve the remainder of the request. It usually does this instantly, and the information is forwarded to the user's PC.

The DNS: A Huge Distributed Database

Millions of people make changes to the DNS every day, through new domain names, changes to IP addresses and other requests. The unique structure of the DNS, though, keeps everything straight. Duplicate domain names cannot exist within domains, but they can exist across them – for instance, example.com and example.gov could be two separate locations online. Otherwise, the highly organized and efficient nature of the DNS ensures that you never have to worry about arriving at two different places each time you input a domain name. When you enter a domain name, its IP address will be resolved and you'll always arrive at the same place. Without the DNS, the Internet wouldn't be useful, practical or enjoyable.