What is a DNS server? How Domain Name System servers connect you to the internet

A DNS server helps your web browser connect to websites.

Photographer, Basak Gurbuz Derman/Getty Images

• A DNS server – short for Domain Name System server – converts web addresses into IP addresses. 
• Without a DNS server, you won't be able to connect to any websites.
• If you're having issues with your default DNS server, you can change it.
• Visit Insider's Tech Reference library for more stories.

A Domain Name System (DNS) server is a fundamental part of the backbone of the internet - without it, it would be impossible to use a web browser to find websites.

You can think of the DNS server as a phone book. When you ask your computer to load a website, the DNS server matches the website's name with the right IP address. This lets your computer find and load it properly.

How does a DNS server work?

When you enter a URL, what you're really doing is asking your computer to find and connect to another IP address. To do this, it uses a set of related servers, all of which form the DNS server:

• The DNS recursive resolver
• The root nameservers
• The TLD nameservers
• The authoritative nameservers

Here's how it works.

The DNS process, step-by-step

1. You ask your web browser to load a website. Since computers don't speak English, your browser can't read a name like "www.insider.com" and instead needs an IP address. Because of this, it sends your request to a DNS recursive resolver. The DNS recursive resolver's goal is to find the IP address connected to the website you entered. 

2. The resolver's first step is to find the website's "Top Level Domain" or "TLD" - in other words, whether it's a .com, .net, .org, or another type of site. It does this by asking the root nameserver, which keeps a list of every website in each TLD.

3. Once the resolver knows the TLD, it goes to the corresponding TLD nameserver (for example, the .com nameserver) and asks it to find the right IP address.

4. The TLD nameserver finds the IP address and hands it off to the authoritative nameserver, which will figure out if that address is correct.

5. The authoritative nameserver sends a message to the address and waits for a response - if it gets the right response, then it has the right IP address for the website you want.

6. If the IP address is correct, the authoritative nameserver sends it back to your web browser.

7. Once your web browser receives the right IP address, your webpage starts to load.

Your web browser goes through a number of steps to load a website.

Alyssa Powell/Insider

All this happens in a matter of seconds - if your internet is very fast, or you've visited the website recently (see below for more information), it can happen in milliseconds.

Caching can avoid calling the DNS server

If you're visiting a new website, your browser will go through the entire process outlined above. But if it did this for every single website, things could get slow - that's why websites you've visited recently are stored in your web browser's cache.

When you try to load a website, the DNS server will first check your cache to see if the IP address is already saved there. If it is, it'll retrieve the IP address directly from the cache, which saves time. 

Every browser has a cache, which stores files and images.

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Each entry in the cache has a time limit associated with it, referred to as the TTL (time-to-live). The TTL for any IP address is generally about 48 hours, and once that passes, the IP address will disappear from your cache. This means that the DNS server will have to go through the whole recursive search process again.

Changing your DNS server

As a general rule, your web browser uses a standard, public DNS server, usually configured and maintained by your internet service provider.

Some advanced users manually change their DNS server, though. This can boost your internet speed and protect your privacy.

Changing your DNS can be done via your computer's "Network" menu, in the Settings app. If you're looking for a new DNS, you can try the Google Public DNS or any number of other custom DNS servers.

Google operates its own DNS server, which you can connect your computer to for free.

Google

Related coverage from Tech Reference:

• How to boost your internet speed at home in 8 ways, and make sure you're not being overcharged for low speeds
  

• How to clear your cache in Internet Explorer and speed up your browsing and loading speeds

• How to clear the cache on a Google Chrome browser to make it run more efficiently

• How to clear the cache on a Safari browser to make it run more efficiently

• 'Why isn't my internet working?': How to identify why you can't connect to the internet and troubleshoot accordingly

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