Glossary

DNS

Definition: Domain Name System — the internet's distributed directory that translates human-readable domain names into IP addresses.

The Domain Name System (DNS) is a hierarchical, distributed naming system that translates domain names (like example.com) into IP addresses (like 93.184.216.34). Without DNS, users would have to memorise numeric addresses for every website they visit.

The DNS Lookup Process

  1. You type example.com in your browser.
  2. Your OS checks its local cache. If found, done. If not…
  3. Your device queries a recursive resolver (usually your ISP's or a public resolver like 8.8.8.8).
  4. The resolver queries a root name server for the TLD (.com).
  5. The root server refers to the TLD name server for .com.
  6. The TLD name server refers to the domain's authoritative name server.
  7. The authoritative server returns the IP address.
  8. The resolver caches the result and returns it to your browser.

Why DNS Matters

  • Every website visit, email sent and API call depends on DNS.
  • DNS outages can take entire services offline (Fastly, Cloudflare DNS outages in 2021).
  • Misconfigured DNS can cause email delivery failures, site downtime and security vulnerabilities.

DNS Record Types

DNS stores information in typed records: A (IPv4 address), AAAA (IPv6), CNAME (alias), MX (mail), TXT (text/verification), NS (nameservers), SOA (start of authority), CAA (certificate authority authorisation).

Check any domain's DNS records with the free DNS Lookup tool.

Free Tools