DNS, the Domain Name System, is the internet's phonebook. You type a domain name, DNS looks up the server address behind that name, and your browser connects. Without DNS, every website would be an IP address you had to memorise.
How a lookup works
When you open a domain, your device asks a resolver, which follows the chain: the root, the extension's servers, then the domain's nameservers. The nameservers answer with the domain's records, and the browser connects to the address in the answer. The whole chain usually takes milliseconds, and results are cached along the way so repeat visits are faster.
The records that matter
- A record. Points the domain to the website server's address.
- MX record. Points mail for the domain to the mail server.
- TXT record. Carries verification and security values, including SPF and DKIM for email.
- CNAME record. Points one name to another name, often used for subdomains and hosted services.
Our guide to checking DNS records shows how to read all four for any domain.
Nameservers and propagation
Nameservers are the servers that hold a domain's records; see what a nameserver is. When nameservers or records change, the new values take time to spread, because caches around the world expire at different speeds. That delay is propagation, covered in how long DNS propagation takes. If a domain stops resolving after a change, work through how to fix DNS resolving errors.
DNS and email
DNS also decides whether your email works. MX records route incoming mail, while SPF, DKIM and DMARC records prove outgoing mail is legitimate. A domain with correct website DNS but broken mail DNS will show a fine website and failing email, so check both. See SPF, DKIM and DMARC explained.
DNS is invisible when it works and confusing when it breaks. Knowing the chain, records and propagation turns most DNS problems into a short checklist.