Have you ever wondered what happens when you use the internet? How does your computer know where to go to find the website you searched for?
The internet uses “IP addresses” to identify servers and devices. All websites are “hosted” on a server, and our devices need to know the address of the server to reach the website.
This is made possible by the Domain Name System (DNS). The DNS is a system of distributed servers that contain information about all registered domain names. Domain names are the recognizable website names that you use to search for them. For example, ‘google.com,’ ‘facebook.com,’ or ‘apple.com.’
The DNS translates the domain name (easily remembered by humans) into the IP address (used by computers) and tells it to your device. This way, your device is able to find the correct website.
This brief, high-level overview should have raised more questions than it answered. We will answer all of them in due time.
In this article, we’ll explain what DNS is, explore the components that make it work, and then walk through the process of a DNS lookup. By the end, you’ll have a clear picture of how DNS quietly keeps the internet running in the background.
What is DNS?
The Domain Name System (DNS) is often described as the Internet’s “phonebook.” As you know by now, its purpose is to translate human-readable domain names (like example.com) into IP addresses that computers and servers use to identify one another. This is done via a process called DNS resolution (more on that later).
Without DNS, human users would need to know the numerical address of every website they wanted to visit. That’s kind of impossible, or at the very least, extremely impractical. With DNS, people only need to remember the domain name of a website to find it.
So, that’s the basic version. To learn more about the Domain Name System, we have to check out its components as well as how the whole DNS resolution process works.
Components of DNS
As we said at the beginning of the article, DNS is a system of distributed servers. There is a hierarchy among them that ensures queries are handled in an orderly fashion. Let’s check these out.
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Recursive Resolver
The recursive resolver is the first DNS server that your device encounters when it is querying the DNS for a domain’s IP address. The resolver’s job is to query the rest of the DNS servers in the hierarchy and find the IP address and return it to your device/computer.
A resolver is usually provided by your ISP, but you can set a different resolver, such as Google DNS, Cloudflare DNS, or Quad9, through your device’s network settings.
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Root Name Servers
The next server in the hierarchy is called the root server. The root servers are technically at the top of the hierarchy. They don’t have the full IP addresses of any domain, but they know which server to ask when the resolver comes to it with a query.
For example, if you are trying to visit a website whose URL has “.com” or “.net” in it, then the root server will send the query to the TLD server, which has information on the “.com” or “.net” TLDs.
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TLD Name Servers
TLD stands for Top-Level Domain. It refers to all domains like “.com”, ‘.org”, “net”, and even country-specific ones like “.jp” or “.uk.”
The Top-Level Domain (TLD) servers manage these extensions. They act as regional directories, narrowing down your request to the correct authoritative name server. Once the query comes to the TLD server, it checks which authoritative name server has the information on the domain name. It then sends the resolver to that server.
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Authoritative Name Servers
The authoritative name server is the final server in the hierarchy. It holds the complete information regarding a domain, including its IP address. This information is stored in the form of files called “DNS records.”
When the query reaches this server, it finally gets the answer from the DNS records and sends it back through the chain or directly to the resolver.
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Caching
To speed things up, DNS uses caching at multiple points. Your browser, operating system, resolver, and even the other DNS servers all keep temporary copies of DNS answers. The duration is determined by a value called TTL (Time to Live). Thanks to caching, repeat visits to the same site happen much faster.
We will discuss caching in more detail later. Let’s move on to discussing how the DNS resolution happens.
How DNS Works (Step-by-Step)
Now that we know the components, let’s walk through what happens when you type www.example.com into your browser.
- Query Initiation. Your browser checks its own cache. If it doesn’t have the answer, it asks your operating system. If the OS doesn’t know, the query is sent to the recursive resolver.
- Recursive Resolver. The resolver checks its cache. If it doesn’t find the IP, it contacts the root server.
- Root Server. The resolver asks a root server, which points it to the appropriate TLD server.
- TLD Server. The TLD server narrows the search and sends the resolver to the authoritative name server for example.com.
- Authoritative Server. This server provides the final IP address for example.com.
- Response & Caching. The resolver delivers the IP back to your computer, which then uses it to connect to the website. The result is cached locally for faster access in the future.
All of this happens in milliseconds, invisible to the user, but it’s what makes web browsing seamless.
Recursive vs. Iterative Queries
Not all DNS queries work the same way. There are two main styles:
- Recursive Query: In this mode, the resolver does all the work. Your computer asks once and authorizes the resolver to keep querying until it finds the answer. This is the standard method used by most internet connections today.
- Iterative Query: In this mode, the computer has to ask the resolver to query the DNS hierarchy every time. For example, the resolver will check its cache; if it doesn’t have the records, it will tell the computer, which will then instruct it to query the root server. Then the root server will return the IP of the TLD server. The computer will then again instruct the resolver to query the TLD server and so on.
Today, we mostly use recursive querying because it is faster and more convenient.
DNS Caching
The entire DNS resolution process, as you have seen, is a bit of a slog. It does happen in milliseconds, but if you have to do multiple resolutions back to back, the milliseconds add up and make you feel as if the internet is slow.
With caching, instead of repeating the entire lookup process every single time, DNS results are temporarily stored at multiple layers so they can be reused. This makes web browsing much faster and reduces the load on servers.
Where DNS is Cached
There are multiple places where DNS cache data is stored. Some of the most common places are listed below.
- Browser Cache
Your web browser keeps a short-term memory of DNS lookups. If you visit the same site again during that period, the browser will connect instantly without asking the resolver again.
- Operating System Cache
Your computer’s OS also stores DNS results. The browser will ask the OS for cache results before going to the resolver. This happens if the browser’s own cache has expired. Operating system services that don’t rely on browsers also use the OS’s DNS cache.
- Resolver Cache
The recursive resolver provided by your ISP or a public DNS service (like Google DNS or Cloudflare) also caches results. Since thousands of users may query the same sites, resolver caching provides a major performance boost across the network.
Time to Live (TTL)
Every DNS record includes a Time to Live (TTL) value. This tells caches how long they’re allowed to store the record before discarding it and requesting a fresh lookup. TTL values are given in seconds, and they can range from a few minutes to a few hours.
Benefits of Caching
We have mentioned the benefits of caching before, but here is a proper list that you can consult.
- Faster browsing and reduced latency.
- Less traffic across the DNS system. This makes the ongoing queries faster because there are no wait times.
- Better resilience. Cached DNS records can sometimes keep sites reachable even if a DNS server is temporarily unavailable.
Why DNS Matters
DNS isn’t just about convenience; it’s critical to how the internet functions. If the DNS system were to go down for any reason, the entire Internet would be unusable.
Performance Impact
A bad DNS system directly impacts how the internet feels. It can make websites feel unresponsive due to long resolution times. Faster DNS resolution means websites load more quickly, and the internet feels snappier.
That’s why switching to a faster DNS resolver can reduce latency and improve browsing speed.
Security Importance
DNS is also a target for attackers. Techniques like DNS spoofing or cache poisoning can mislead users into visiting malicious websites. Security extensions such as DNSSEC (Domain Name System Security Extensions) were introduced to protect against these threats.
Reliability
The global network of DNS servers is massive to ensure redundancy. For each domain, there are multiple nameservers. All the other servers in the hierarchy also have multiple copies.
If one server goes down, others pick up the slack, keeping the internet resilient.
Common DNS Issues
Since DNS is such a central system, any problems with it can impact a lot of people. Given below is a list of common DNS issues that can make websites feel slow, unavailable, or even result in security flaws.
Propagation Delays.
When DNS records are updated, the changes can take hours to fully spread across the internet. This is called the DNS propagation delay. It is caused by caching. Until DNS servers expire their cached records, they won’t check for new ones. This can be handled by lowering the TTLs on DNS records so that they aren’t cached for too long.
You can monitor propagation delays for your domain using DNS checking tools. DNS checking tools can also show a variety of other useful information and are great for verifying your own domain’s DNS setup. Our DNSChecker.org provides a complete set of these tools that you can use for free.
Stale Cache Data.
Stale cache is when a DNS server or your computer/OS has an old version of a DNS record stored, while a new one has already been published. It will try to use the old records to complete the DNS resolution, and the outdated information will result in an error. For example, if a domain’s IP changes but your cache hasn’t expired, you may be directed to the old server, which no longer has the website, and you will see a website-unavailable error.
DNS Cache Poisoning.
Hackers can poison cached data if the device that has the cache is not secure enough. For example, attackers can insert false DNS records into a cache, redirecting users to fraudulent sites. This has been largely solved by DNSSEC, a DNS security protocol that detects and warns about DNS record tampering.
Misconfigurations.
If you are a webmaster, incorrect DNS settings for your domain (such as wrong nameserver entries) can make your website inaccessible. So proper care is required to ensure your website remains live and accessible.
Conclusion
The Domain Name System is one of the Internet’s most essential foundations, quietly working in the background every time you go online. By translating human-readable names into machine-readable IP addresses, DNS ensures that the internet remains usable and scalable.
