Learn what a DNS lookup is, how domain names become IP addresses, which DNS records matter, and when to use a DNS lookup tool.

Quick wins from this guide
  • Understand what DNS tools are showing you
  • Know which record type to check first
  • Troubleshoot website and email issues faster

What a DNS lookup does

A DNS lookup asks the Domain Name System for information about a domain name. In everyday terms, it answers questions such as “which IP address should this website load from?”, “which servers handle email for this domain?” or “which nameservers are authoritative for this domain?”. DNS is often described as the internet’s address system because people remember names like example.com, while computers need IP addresses and other routing details.

Why DNS lookups matter

When a website does not load, mail bounces, a domain points at the wrong server or a new record does not appear to work, a DNS lookup is usually one of the first checks to run. It lets you separate DNS issues from web server issues. If the A record points to the wrong IP address, no amount of WordPress tweaking will fix the problem. DNS first, panic later.

Common record types to check

For websites, start with A and AAAA records. For aliases, check CNAME records. For email, check MX records and TXT records used for SPF, DKIM and DMARC. For delegation, check NS records. When you know the purpose of each record, the output from a DNS lookup stops looking like alphabet soup and starts looking like a checklist.

Web tool or command line?

A web DNS lookup tool is quick and convenient. Command line tools such as dig, host and nslookup give you more control, especially when comparing resolvers or checking authoritative nameservers. If you want to practise the command line side, the CommandLineQuiz dig Command Builder is a useful next step.

Quick commands to try

dig example.com A
dig example.com MX +short
host -t TXT example.com

Practise the command line side

DNSNow gives you quick web checks. For hands-on Linux command practice, use CommandLineQuiz dig Command Builder, the Linux Troubleshooting Hub and the Bash Scripting Hub.

FAQs

Is a DNS lookup the same as a WHOIS lookup?

No. A DNS lookup checks records used to route websites, email and services. A WHOIS lookup checks registration information, registrar details and domain status where available.

Which DNS record should I check for a website?

Start with A records for IPv4 and AAAA records for IPv6. If the hostname is an alias, also check the CNAME record.

Can DNS lookups show email settings?

Yes. MX records show mail exchangers, while TXT records often contain SPF, DKIM and DMARC information.

Sources and further reading