What Is DNS? How the Domain Name System Works

The domain name system (DNS) is essential for web browsing, yet few understand how it works. Have you ever wondered how web browsers manage to sort the internet’s vast documentation to serve you with the right pages? Then this article is for you. 

What is DNS?

The domain name system (DNS) is a universally recognized mechanism that identifies and locates all pages and content reachable through the web. It translates and connects a human-readable URL (such as shopify.com) to a machine-readable number, known as an IP address (such as 23.227.38.65). A user’s browser uses this IP address to retrieve a site’s content.

“DNS is used for lots of less obvious things, too: connecting a domain to an email provider (e.g., Fastmail, Google Workspace, etc.), confirming ownership of a domain (e.g., for federated social media), and much more,” adds Dave Smyth, independent UX/UI designer.

The DNS was created in 1983 by Paul Mockapetris and Jon Postel as part of the ARPANET project. At the time, computers could only communicate using numbers, and a browser needed a website’s IP address to access it. The DNS became the connection, acting as a virtual phonebook of domain names and their corresponding IP addresses.

How does DNS work?

DNS is like a phone book for the web. It locates and serves you the pages you seek through a rapid, complex series of internet protocols. When you type a URL into a web browser, the DNS translates it into a unique internet protocol (IP) address, similar to a phone number. Every device that’s connected to the internet—whether you use it to host websites or browse them—has an IP address.

What is a DNS query?

A DNS query (or a DNS request) is a request for information sent from a user’s device (called the DNS client) to a DNS server. The most common type of DNS query is a request for the IP address associated with a specific domain. 

For example, if you wanted to visit shopify.com, your computer would send a DNS query to a DNS server to ask for the site’s IP address. The DNS server replies with the IP address that your computer uses to connect you with the Shopify website. All of this happens within seconds.

What is a DNS server?

A DNS server is a computer that converts domain names into IP addresses and is a crucial component of the internet. A browser sends a request to the DNS server to find a domain’s IP address, and then you land on the intended website. 

A DNS server works through a process called DNS resolution. A client, a.k.a. a user device, issues a DNS query for an “A record,” essentially a map that connects a domain name to an IP address. There are four types of DNS servers involved in loading a webpage: 

1. A DNS recursor (also called a recursive resolver)
2. Root name servers
3. Top-level domain (TLD) nameservers
4. Authoritative nameservers

DNS recursor

A DNS recursor (or recursive resolver) is the first step in a DNS query. Imagine a recursive resolver as the front desk attendant of a large archival warehouse. They receive DNS resolver queries from your browser, then send their own DNS requests to several other servers to locate the information you’re looking for. 

Root name server

The root name server is the first server the recursor queries during the DNS lookup process. A DNS root name server receives requests from a recursor and responds with a list of top-level domain (TLD) nameservers that contain the information the recursor is looking for. 

TLD name server

A TLD name server is responsible for maintaining information for all domains that share a common extension (such as .com or .net), known as a top-level domain. After receiving a response from the root name server, the DNS recursor queries the appropriate TLD name server, which responds with the appropriate authoritative name server. 

Authoritative name server

An authoritative name server answers the DNS recursor’s initial query, replying with the webpage’s IP address—or, if it can’t find it, with an error message.

Once the resolver has a corresponding IP address for the requested webpage, it can send the information to the web browser, which can then display the requested web page.

What is the difference between a DNS and an IP address?

A DNS translates the domain name requested by a user into an IP address. The IP address is the numeric location of the files belonging to that domain. 

What is DNS caching? 

When a DNS client stores DNS records locally, it’s called DNS caching. Caching lets clients produce information about web pages associated with given domain names without having to perform DNS queries. 

The domain name system also implements a time-to-live (or TTL) on all DNS records, which specifies how long clients can cache records. TTL values are stored during the caching process, enabling records to delete themselves from the cache once the specified period has passed.

What are the types of DNS queries? 

There are three types of DNS queries: recursive, iterative, and non-recursive.

Recursive query

In a recursive query, a DNS client provides a hostname and requires the recursive DNS server (DNS resolver) to respond with the correct resource records or an error message saying the records could not be retrieved.

Iterative query

In an iterative query, a DNS client provides a hostname and allows the DNS resolver to return the best answer it can. The DNS resolver may respond by returning cached DNS records (if it has them) or by referring the DNS client to the root server or an authoritative DNS server nearest to the required DNS zone. 

The recursor then queries the provided DNS name servers for a match. This process continues down the server chain of command until an answer, error, or timeout occurs. 

Non-recursive query

In this type of query, the DNS resolver provides an immediate answer, either because it’s authoritative for the record or because it has the record stored in its cache. In non-recursive queries, there is no need for additional queries since a response can be returned immediately. 

What are the steps in a DNS lookup? 

A DNS lookup is a process that your computer uses to find the IP address of a domain. Here’s how the process works:

1. You type a website address (e.g., www.shopify.com) into your browser.
2. Your computer checks its local cache. If you’ve visited the site before, your browser likely remembers the IP address, skipping this process and taking you directly to the IP address.
3. If the address isn’t in your cache, it sends a request to the DNS recursive resolver.
4. The DNS recursive resolver responds with the IP address for the site’s TLD and makes a request to the domain server.
5. The authoritative DNS server shares the IP address of the site.
6. The IP address is passed from the DNS resolver back to your computer.
7. You can access the website.

What is a CNAME record?

A canonical name (CNAME) record is used in the DNS lookup process for creating an alias from one domain name to another.

For example, a DNS client trying to resolve the subdomain name www.example.com would be referred to the root domain (in this case, example.com) by a CNAME record. 

Some common uses for CNAME records are:

• Redirecting users from owned domains to the primary website. For example, typing the URL gogle.com will redirect users to google.com, despite the spelling error.
• Providing separate hostnames for specific network services running on different ports—for example, allowing a file transfer protocol (FTP) server and a web server to run on different ports from the same IP address.
• Registering localized domains and pointing them to a primary website. For example, if your primary website was hosted at example.com and you wanted to redirect users from example.ca, example.co.uk, and example.us to the same website.

The DNS is an essential part of browsing the internet

Browsing the internet wouldn’t be possible without the domain name system (DNS)—every internet service provider uses it. The virtual equivalent of a phonebook, the DNS connects domain names with IP addresses, leading users to their desired websites. 

If you’re buying a domain for your new project, opt for a registrar that makes DNS management easy. Shopify, for example, lets you edit the DNS settings from your Shopify-managed domain without leaving the ecommerce platform, giving you one less thing to worry about when you’re selling online.