What is DNS and how does it resolve domain names?

Short answer

DNS (Domain Name System) is the internet's phonebook. It translates human-readable domain names like example.com into machine-readable IP addresses that computers use to identify each other.

How it works

When you enter a domain, your device first checks its local DNS cache. If the record is not found, it queries a recursive resolver, which contacts root name servers, Top-Level Domain (TLD) servers, and authoritative name servers in sequence until it finds the matching IP address.

The resolver then returns the IP to your device and caches the result for faster future lookups. This entire process typically completes in milliseconds.

Example

When you visit mail.google.com, DNS finds the A or AAAA record pointing to Google's mail servers. MX records route email, CNAME records create aliases, and TXT records store verification strings.

Why it matters

DNS enables the internet to remain user-friendly. Without it, users would need to memorize numerical IP addresses. DNS also supports load balancing, email routing, and security mechanisms like DNSSEC.