What is a DNS server? How Domain Name System Servers Work

  • A DNS server – short for Domain Name System server – converts web addresses to IP addresses.
  • Without a DNS server, you will not be able to connect to any website.
  • If you’re having trouble 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 name with the right

IP adress

. This allows your computer to find and load it properly.

How does a DNS server work?

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

  • The recursive DNS resolver
  • Root nameservers
  • TLD name servers
  • Authoritative name servers

Here’s how it works.

This all happens in seconds – if your internet is very fast or you’ve recently visited the website (see below for more info), this can happen in milliseconds.

Caching can avoid calling DNS server

If you visit a new website, your browser will go through the whole process described above. But if it did for every website, things might 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 first checks your


to see if the IP address is already registered there. If so, it will fetch the IP address directly from the cache, which saves time.

What is a cache 2

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

Dave Johnson/Business Insider

Each entry in the cache is associated with a time limit, called TTL (time to live). The TTL for any IP address is usually around 48 hours, and once that passes, the IP address will disappear from your cache. This means that the DNS server will have to start the whole recursive lookup process again.

Change your DNS server

Typically, your web browser uses a standard public DNS server, usually configured and maintained by your ISP.

However, some advanced users manually change their DNS server. It can increase your internet speed and protect your privacy.

Changing your DNS can be done through your computer’s “Network” menu, within the Settings app. If you’re looking for a new DNS, you can try Google’s public DNS or a number of other custom DNS servers.

Google Public DNS

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