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How does DNS work?

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Quick answer

DNS, or Domain Name System, translates human-readable domain names like knowit.guru into numeric IP addresses that computers use to locate each other. When you enter a domain name, your device queries DNS servers, which return the corresponding IP address so your browser can connect to the correct server.

DNS (the Domain Name System) is the internet's phone book. When you type a website name, DNS looks up the numeric IP address behind it so your device can connect. It translates human-friendly names like knowit.guru into the addresses computers use.

Step by step

  1. You type a domain name into your browser, which checks its local cache for the corresponding IP address.
  2. If not cached, the query goes to a recursive DNS resolver, often provided by your ISP or a public service like 8.8.8.8.
  3. The resolver queries a root name server, which directs it to the appropriate top-level domain (TLD) server, such as .com or .org.
  4. The TLD server points to the domain's authoritative name server, which holds the actual IP address for the domain.
  5. The authoritative server returns the IP address to the resolver, which sends it back to your browser and caches it for future use.

Key things to understand

  1. It translates domain names into IP addresses.
  2. It's often called the internet's phone book.
  3. Your request passes through DNS servers to find the address.
  4. Results are cached to speed up future lookups.

Labelled diagram

  1. User's Device

    Initiates a DNS query when you enter a domain name in a browser or app.

  2. Recursive Resolver

    Receives the query and searches through DNS servers to find the IP address.

  3. Root Server

    Directs the resolver to the correct top-level domain (TLD) server.

  4. TLD Server

    Points the resolver to the domain's authoritative name server.

  5. Authoritative Server

    Provides the final IP address for the requested domain.

How a DNS lookup resolves a domain name

Real-world examples

  • When you type www.google.com, DNS translates it to an IP address like 142.250.72.196 so your browser can load the search page.
  • Sending an email to someone@example.com uses DNS to find the mail server's IP address via MX records.
  • Streaming a movie on Netflix involves DNS lookups to connect to the nearest content delivery server for smooth playback.
  • Scanning a QR code that contains a URL triggers a DNS query to resolve the domain before the website opens on your phone.

Common mistake

✗ Myth: DNS and the domain registry are the same thing.

✓ Fact: DNS is the system that translates domain names to IP addresses, while a domain registry is an organization that manages domain name registrations for a specific top-level domain, such as .com. They work together but serve different roles.

People also ask

What happens if DNS fails?
If DNS fails, you cannot access websites by their domain names because your device cannot find the corresponding IP addresses. You might see error messages like 'Server not found' or 'DNS lookup failed.' However, you could still reach websites by typing their IP addresses directly, though this is impractical for most users.
What is a DNS server?
A DNS server is a computer that stores a database of domain names and their corresponding IP addresses. It responds to queries from clients, such as your computer or phone, to resolve domain names into IP addresses. There are different types, including recursive resolvers, root servers, TLD servers, and authoritative servers, each playing a specific role in the lookup process.
Why would you change your DNS server?
You might change your DNS server to improve speed, reliability, or privacy. Some public DNS services, like Google DNS or Cloudflare, can offer faster resolution times than your ISP's default. Others provide additional features like filtering malicious websites or blocking ads, enhancing your online experience and security.
How does DNS work?
It looks up the IP address behind a domain name so your device can connect to the right server.
What does DNS stand for?
Domain Name System.
Why is DNS like a phone book?
It maps easy-to-remember names to the numeric addresses computers actually use to find each other.

Part of the guide: How the Internet Works →