A DNS server is a computer that turns a domain name into an IP address. Your device needs that address to reach the website. In other words, the server works like the internet’s address book.

You look up a name, and it hands back the number. Without it, you would type long strings of digits for every site.

This article follows one real lookup from start to finish. By the end, a DNS error message will make sense to you.

What Is a DNS Server?

A DNS server stores or retrieves the records that link domain names to IP addresses. A domain name is the word-based address people remember, such as example.com.

An IP address is a numeric address that computers use, such as 203.0.113.10. Computers route traffic with numbers. People, however, remember words. DNS exists to connect the two.

DNS vs. a DNS Server

People often mix up these two terms. DNS, short for Domain Name System, is the overall system and set of rules that govern how domain names are resolved.

A DNS server is one of the machines that runs it. So DNS is the method, and the server is the hardware doing the work.

DNS Server vs. Name Server

You will also see the term name server. In most articles, it means the same thing as a DNS server.

Technically, a name server stores records for a domain, while a resolver looks them up for you. Both count as DNS servers, so the labels overlap.

What Does a DNS Server Do When You Type a Web Address?

Every time you enter a web address, your device sends a query. The query asks one simple thing: what is the IP address for this domain?

A DNS server does three jobs in response:

• It receives the query from your device.
• It finds the answer, either from memory or by asking other servers.
• It returns the IP address so your browser can connect to the site’s web server.

Once your browser has the address, it contacts the web server and loads the page. The whole exchange usually takes tens of milliseconds.

As a result, you rarely notice it happening. You only notice when it fails, and the page refuses to load.

How Does a DNS Server Work? A Step-by-Step Lookup

The easiest way to see this is to follow one DNS lookup. Say you type example.com into your browser. Here is what happens, in order.

Browser → Recursive resolver → Root server → TLD server → Authoritative server → Answer back to browser.

1. Your browser and device check their caches. Your browser first looks in its own memory. Your operating system keeps a similar cache. If you visited the site recently, the answer is already there. In that case, the lookup ends immediately.

2. The query goes to a recursive resolver. If no cached answer exists, your device asks a recursive resolver. Your internet provider usually runs this server. However, you can also point your device to a public resolver. The resolver checks its own cache first. If it comes up empty, it does the legwork for you and asks other servers until it finds the answer.

3. The resolver asks a root server. The root server doesn’t know the IP address. Instead, it points the resolver to the correct top-level domain server based on the domain’s suffix. For a domain like example.com, the ending is .com. The root system has 13 named addresses, and many machines back each one.

4. The TLD server points to the authoritative server. The top-level domain (TLD) server handles one ending, such as .com or .org. It doesn’t hold the site’s IP address either. What it does know is which server is responsible for example.com. It sends the resolver there.

5. The authoritative server returns the IP address. This server holds the real records for the domain. It checks its records and replies with the IP address, such as 203.0.113.10. At last, the resolver has what it came for.

6. The resolver answers your browser. The resolver saves a copy of the answer and passes it to your device. Your browser then connects to the web server at that address. The page loads a moment later.

This chain sounds long. In practice, it usually finishes in tens of milliseconds. Caching, covered below, shortens most lookups.

Types of DNS Servers

Four types of DNS servers take part in a lookup. Each has a different job.

The recursive resolver is the only one your device talks to directly. The other three work behind the scenes, answering the resolver.

The simplest way to tell the two apart is by job. A recursive resolver looks things up. An authoritative server holds the records.

Resolvers also come in public and private versions. Public ones, like Google’s 8.8.8.8 or Cloudflare’s 1.1.1.1, are open to anyone. Private ones serve a single network, such as a company or an internet provider.

How DNS Caching Makes Lookups Quicker

Caching means a server keeps a recent answer instead of asking again. Most lookups rely on it. As a result, the full chain above runs far less often than you might expect.

Answers get cached in three places:

• Your browser
• Your device’s operating system
• The recursive resolver

The resolver cache helps the most. Many users share it, so popular sites are usually already cached.

Each cached answer carries a timer called TTL, short for time to live. The domain owner sets it, anywhere from a few minutes to a day. When the timer runs out, the server discards the answer and asks again.

This timer explains a familiar frustration. After a site moves to a new server, some visitors still see the old one. Their resolvers simply haven’t discarded the old answer yet. People call this delay propagation, and it ends once every cache expires.

FAQs

Start With Your Own Domain

You can now follow a lookup from keystroke to loaded page. The browser asks, the resolver hunts, and the authoritative server finally answers.

If you run a website, you depend on this system every day. Your domain needs correct DNS records, or visitors can’t reach you.

Ready to put this into practice? Register your domain with Truehost and set up its DNS records today.

/