1. Home
2. Documentation
3. How it works

How Recursive DNS Works

The Domain Name System (DNS) is the backbone of the internet, translating human-friendly domain names (like example.com) into IP addresses that computers use to communicate. Recursive DNS resolvers play a critical role in this process, ensuring fast and reliable access to websites and online services.

What is a Recursive DNS Resolver?

A recursive DNS resolver is a server that handles DNS queries on behalf of users. Instead of knowing the answer immediately, it recursively queries multiple DNS servers to find the correct IP address.

When you type a website into your browser, your computer doesn’t ask a single server for the answer—it relies on a recursive resolver to fetch it from authoritative sources.

How Does Recursive DNS Work?

Here’s what happens when you enter a domain like example.com in your browser:

1. Your device sends a DNS query to a recursive resolver, asking for the IP address of example.com.
2. The resolver first checks its local cache to see if it has a recent answer. If it does, it returns the result immediately.
3. Querying the Root Servers (if no cache hit):
   • The resolver contacts one of the root DNS servers (which manage top-level domain information).
   • The root server responds with a referral to the appropriate Top-Level Domain (TLD) server (e.g., for .com domains).
4. Querying the TLD Server:
   • The resolver contacts the TLD nameserver (e.g., the .com TLD).
   • The TLD server replies with a referral to the authoritative nameserver for example.com.
5. Querying the Authoritative Nameserver:
   • The resolver asks the authoritative nameserver for example.com’s IP address.
   • The authoritative server responds with the correct IP (e.g., 192.0.2.1).
6. Returning the Answer:
   • The resolver sends the IP address back to your device.
   • Your browser connects to the website using this IP.

This process usually happens in milliseconds.

Why is Recursive DNS Important?

Recursive DNS resolvers play a crucial role in making internet browsing faster and more efficient. By caching previous queries, they reduce the need for repeated lookups, meaning that if a user requests the same domain again, the resolver can provide the answer instantly without having to query external servers. This caching mechanism significantly improves browsing speed and overall performance.

In addition to improving speed, recursive resolvers help reduce network traffic. Since they store DNS responses temporarily, they minimize the number of queries sent to authoritative servers, which helps decrease congestion and enhances the efficiency of the global DNS infrastructure.

Security is another critical aspect of recursive DNS. Resolvers that support DNSSEC validation ensure that DNS responses have not been tampered with by attackers. By verifying digital signatures on DNS records, DNSSEC prevents malicious activities like DNS spoofing and cache poisoning, which can redirect users to fraudulent websites.

Finally, recursive resolvers can enhance privacy and security. Trusted resolvers, like those provided by the UK DNS Privacy Project, prioritize user privacy by avoiding logging, preventing third-party tracking, and supporting encrypted DNS protocols such as DNS-over-HTTPS (DoH) and DNS-over-TLS (DoT). Additionally, they can filter out known malicious domains, providing an extra layer of protection against phishing and malware attacks.

Recursive DNS vs. Authoritative DNS

	Role	Data Storage	Who Uses It	Security
Recursive DNS Resolver	Finds answers for clients	Caches responses temporarily	End users (ISPs, public resolvers)	Can validate DNSSEC and filter malicious domains
Authoritative DNS Server	Provides answers for its domains	Stores official DNS records	Website owners, domain providers	Must secure its own records from attacks