What Is DNS? Meet the Quiet Technology Powering the Modern Web

Every time you type a website address into your browser, a complex system works behind the scenes to connect you to that site in milliseconds. This system is called DNS, which stands for Domain Name System. While you probably don't think about it, you use it many times throughout the day.

In this guide, we'll explain what DNS is, how it works, and why it matters for both casual internet users and website owners. We'll also cover how to troubleshoot DNS problems and answer common questions about DNS servers, caching, and lookups.

What is DNS?

DNS stands for Domain Name System, and it acts as a bridge between humans using the internet and the underlying hardware that powers it. Put more accurately, it's a conversion service that switches domain names into IP addresses and vice versa.

DNS exists because, without it, humans would need to use the internet the same way computers do — by remembering long strings of numbers (i.e., IP addresses) to access websites. This is exactly how computers find each other on the web. For us mortals, though, it’s neither practical nor very convenient for branding or business purposes.

Here's how DNS works:

1. Whenever you type a website address, such as youtube.com, into your browser, your request travels to a DNS server.
2. That server looks up the domain name in its directory.
3. The DNS server resolves the domain name to an IP address and returns it to your browser.
4. The server uses that IP address to load the website.

All of this happens in a fraction of a second, which is almost unbelievable when you consider that in some cases your DNS request involves multiple servers talking to each other. Let’s talk about that next.

Types of DNS servers

When you make a DNS request, your query doesn't just ping one server and call it a day — at least not the first time. It actually passes through four different types of DNS servers, each with a specific role in the DNS lookup process.

Recursive resolver (or DNS recursor)

This is the “head honcho” that runs the whole show. When your browser asks "What's youtube.com?", the recursive resolver queries the other three server types in sequence — root, TLD, then authoritative — each narrowing the search until it finds the exact IP address.

It also caches results for a specific amount of time (defined by the time-to-live or TTL value), so repeated requests don’t have to run through that sequence. They are served instantly as long as they fall within the TTL.

Root nameserver

If the recursive resolver doesn't have the answer cached, it contacts a root nameserver. There are 13 root name server systems worldwide (labeled A through M) that sit at the top of the DNS hierarchy. [1] Their job is to direct queries based on domain extension. For example, if you type in allaboutcookies.org into your browser, the root server directs the query to the .org TLD nameserver.

TLD nameserver

TLD stands for Top-Level Domain and refers to the last part of a domain name (e.g., .com, .org, .net). The TLD nameserver maintains information for all domains under its extension. It doesn't have the final IP address either, but it knows which authoritative nameserver is responsible for the specific domain you're looking for.

Authoritative nameserver

This is where the actual IP address lives. Website owners manage their DNS records here, making it the source of truth for where a domain points. The recursive resolver retrieves the correct IP address from here and returns it to your browser.

The entire journey typically happens in milliseconds, which is why DNS feels instantaneous, even though the recursive resolver often makes multiple stops if it doesn't already have an IP cached.

Troubleshooting DNS server errors

DNS problems can manifest in several ways, from your browser displaying "DNS server not responding" to connection timeout errors. Understanding how to diagnose and fix these issues can save you significant troubleshooting time.

Common DNS error messages

When DNS fails, you'll typically see browser error messages like:

DNS_PROBE_FINISHED_NXDOMAIN = The domain name doesn't exist or cannot be found 

DNS_PROBE_FINISHED_NO_INTERNET = Your device can't reach DNS servers 

Server DNS address could not be found = DNS lookup completely failed 

DNS server not responding = Your configured DNS servers aren't reachable

How to fix common DNS errors

If you're experiencing DNS errors such as the ones above, try these troubleshooting steps in order:

1. Check your internet connection. Basic connectivity issues often masquerade as DNS problems. If you can't load any websites, verify your Wi-Fi or Ethernet connection is active.
2. Flush your DNS cache (see the How DNS caching works section below for instructions).
3. Try a different DNS server. Switch from your ISP's DNS to a public alternative, such as Google DNS (8.8.8.8 and 8.8.4.4) or Cloudflare (1.1.1.1).
4. Restart your router and modem. Unplug for 30 seconds, then reconnect.
5. Disable VPN or proxy temporarily. These services can interfere with DNS resolution or even cause DNS leaks.
6. Check if the website is actually down. Use a free service like Is It Down Right Now, or try accessing the site from a different device or network. The problem might be with the website itself, not your DNS.

How to do a DNS lookup

There are several reasons you might need to perform a DNS lookup. These include migrating to a new host, troubleshooting site accessibility issues, or verifying that DNS changes have propagated across the internet.

You might also want to confirm which IP address a domain currently points to. There are two straightforward ways to do it:

1. Use a free online DNS lookup tool: Beginner-friendly websites like MXToolbox, WhatsMyDNS, or DNSChecker let you enter a domain name and instantly see its DNS records.

2. Use your computer’s command line tool: If using Windows, open Command Prompt and type in nslookup domainname.com. For Mac/Linux users, open Terminal and either type in the same nslookup domainname.com command, or for a more detailed response, use the dig domainname.com command instead.

How to find your own DNS server

Finding your own DNS server is a slightly different process from doing a DNS lookup on a domain.

If you want to see which DNS servers your computer is currently using (whether that's your ISP's servers or a public service like Google DNS), you can check your network settings or use the command ipconfig /all (on Windows) or scutil --dns | grep nameserver (on Mac).

This shows you the DNS servers handling all your internet requests, which can be useful when troubleshooting slow browsing speeds or connectivity issues.

How DNS caching works

DNS caching temporarily stores lookup results so your computer doesn't need to query DNS servers every time you visit a website. This happens at two levels: your web browser and your operating system.

• Browser-level caching is when your browser (e.g., Chrome or Safari) stores DNS results for a short period, typically minutes to an hour. This cache clears when you close your browser or manually clear your browsing data.
• OS-level caching runs deeper. Your operating system caches DNS lookups for all applications, not just your browser, and those caches persist longer.

Understanding how caching works and that it happens at two levels helps you troubleshoot effectively.

For example, if you're seeing outdated page content on a website, try tapping Command + Shift + R (on a Mac) or Ctrl + Shift + R (with Windows) on your keyboard to force a hard refresh. While this doesn't actually flush your browser cache, it simulates it on the web page you're on. The result for you is the same: you'll see the current version of the page.

However, if the issue is DNS-related (your computer is resolving the domain to the wrong IP address), you'll need to flush your OS-level cache. You can do this by typing the following commands into your command line tool: ipconfig /flushdns (on Windows) or sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder (on Mac).

Why does DNS matter?

The reality is that without DNS, we'd be stuck using the internet the same way computers do — by relying on IP addresses to find websites. Since IP addresses are strings of numbers, having to type an IP address to access a web page would be unfathomable.

Thanks to DNS, we can use memorable domain names instead. That makes DNS the unsung hero of the modern web.

For website owners, understanding how DNS works is important, as a site's nameservers must be properly configured with accurate DNS records. A misconfigured DNS setting can make a site completely inaccessible, even if everything else is working perfectly.

The good news is that most of the time, DNS just works its magic in the background, so you don't even have to think about it. However, if something does happen, you now have the knowledge to diagnose and fix the problem.

Bottom line

DNS forms the backbone of the modern internet, but despite relying on it constantly, most people don't even know it exists. But now that you've learned how it works, you can also troubleshoot DNS-related issues when they arise.

For example, if you're experiencing slow load times or connectivity issues, you can switch to a public DNS service, such as Google DNS or Cloudflare. Or if a website doesn't load correctly after an update, knowing how to flush DNS can often resolve the issue.

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