DNS for people who have just bought a domain

You own the name. Now something has to connect it to a server, and that something is DNS: a distributed directory mapping names to addresses and other information. In practice you will edit six kinds of entry.

NS — who is in charge

Nameserver records say which servers hold the authoritative answers for your domain. They are set at the registrar, and they are the switch that determines where every other record is read from.

Change these and everything else changes with them. If you move DNS hosting, create the records at the new provider first, confirm they are correct, and only then switch the nameservers — doing it the other way round takes the site down while you type.

A and AAAA — where the site lives

An A record maps a name to an IPv4 address; AAAA does the same for IPv6. This is the record that makes yourname.com load a website.

The most common oversight: creating the record for www and forgetting the bare name, or the reverse. Both forms should resolve, with one redirecting to the other so only one serves the site.

CNAME — an alias

Points one name at another name rather than at an address. Useful for subdomains handled by a third party, and for a wildcard that catches every subdomain you have not defined.

The rule that catches people: the root of a domain cannot normally carry a CNAME. That is why the bare name needs an A record even when every subdomain is an alias. Some providers offer a workaround under a different name.

MX — where email goes

Tells other mail servers which machines accept mail for your domain, with priorities. Separate from your website: mail and web can live on entirely different providers, and usually do.

Deleting MX records during a hosting change is the classic way to silently stop receiving email. Nothing bounces visibly to you; senders get failures you never see.

TXT — arbitrary text, mostly for email

Used for domain verification and, more importantly, for the three email authentication records that decide whether your mail reaches inboxes. Without them, mail sent from your domain is much more likely to be treated as suspicious.

Set all three properly when you set up email. It is an hour once, and it determines deliverability permanently.

TTL — how long answers are cached

Every record carries a lifetime telling resolvers how long to remember it. Long values mean fewer lookups; short values mean changes take effect faster.

The practical use: lower the TTL a day or two before a planned migration, so that when you switch, the change propagates in minutes rather than hours. Raise it again afterwards.

Three mistakes worth avoiding

Changing nameservers before the records exist at the new provider. Deleting mail records while reorganising web records. And assuming a change is broken because your own machine still shows the old answer — caching is per-resolver, so check from more than one place before concluding anything.