The phonebook analogy

DNS — the Domain Name System — exists because computers navigate the internet using numeric IP addresses, and humans don't remember those well. DNS is the lookup layer that turns a name like traxio.co.uk into the address a server actually needs, the same way a phonebook turns a person's name into a phone number.

Every domain has a set of DNS records that tell the internet where to send different kinds of traffic — the website, the email, and anything else attached to the name. Understanding four or five record types covers almost everything you'll ever need to change.

A records: where the website lives

An A record points a domain (or subdomain) at a numeric IPv4 address — the specific server your website is hosted on. This is the record you change if you move hosting providers but keep the same domain: update the A record to the new server's IP address and, once it propagates, traffic starts arriving at the new host instead.

An AAAA record does the same job for IPv6 addresses, the newer and much longer address format gradually replacing IPv4.

CNAME records: aliases

A CNAME record points one domain name at another domain name rather than an IP address directly — commonly used for something like 'www.traxio.co.uk' pointing at 'traxio.co.uk'. This means if the underlying IP address ever changes, only the one A record needs updating rather than every alias individually.

MX records: where email goes

MX (Mail Exchange) records tell the internet which server handles email for a domain — separate from whichever server hosts the actual website. This is why a domain can be hosted with one company and have its email handled by another, entirely independent of each other, as long as the MX records point to the right place.

Each MX record has a priority number; lower numbers are tried first, which is how a domain can have a primary and backup mail server configured at once.

TXT records and propagation

TXT records store arbitrary text attached to a domain and are most often used for verification — proving domain ownership to a service like Google Workspace, or publishing SPF and DKIM records that help prevent email sent from your domain being marked as spam.

Whenever a DNS record changes, it doesn't update everywhere instantly. Propagation is the term for that spreading process, and it typically completes within a few hours, though it can occasionally take up to 48 hours depending on how the record's time-to-live (TTL) was configured beforehand.