DNS turns names people can remember into the addresses computers use. When it is configured well nobody notices it, and when it breaks nothing works. Here are the records you will meet most often.
The common record types
| Record | What it does |
|---|---|
| A | Points a name to an IPv4 address |
| AAAA | Points a name to an IPv6 address |
| CNAME | Makes a name an alias of another name |
| MX | Says which mail servers accept email for the domain |
| TXT | Holds text, often used for email authentication and ownership checks |
| NS | Lists the authoritative name servers for the domain |
| CAA | Restricts which certificate authorities may issue certificates |
| SOA | Holds zone details such as the serial number |
A and AAAA
These are the simplest records. www.example.com has an A record with an IPv4 address and, if you support IPv6, an AAAA record with an IPv6 address. Visitors reach whichever address their network prefers.
CNAME
A CNAME does not hold an address. It says that one name is an alias of another, and resolvers then look up the target name. It is commonly used to point www or a subdomain at a hosting provider. A name that has a CNAME cannot also carry other records, which is why a CNAME is usually not allowed at the root of a domain.
MX and TXT
MX records route email, with a priority number so that a backup server can take over. TXT records carry text, and are used for SPF, DKIM and DMARC email authentication, as well as for proving you own a domain to another service. A mistake here rarely takes your website down, but it can quietly send your email to spam.
What TTL means
Every record has a time to live, or TTL, in seconds. It tells resolvers how long they may cache an answer. A long TTL reduces lookups, but changes take longer to reach everyone. Before a planned migration, many teams lower the TTL a day or two ahead so the switch propagates quickly, then raise it again afterwards.
Which changes are worth monitoring
- A and AAAA records for your main hostnames, in case traffic is redirected
- MX and TXT records, in case email delivery breaks
- NS records, because a change there moves control of the whole zone
- CAA records, if you restrict certificate issuance
Tip. Keep a history. When something stops working, the first question is usually what changed, and a record of past values answers it quickly.
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