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DNS Record Types Explained: A, AAAA, CNAME, MX, TXT and the Rest
A DNS zone is a lookup table. Each record type answers one question about a name, and most confusion comes from expecting a type to answer a question it was never designed for.
Run a fresh DomainLens audit and use the report as your priority list.
DNS records explained in one table
Every record maps a name to a value, and the type says what kind of question the value answers. Nine types cover almost everything you will meet.
| Type | Answers | Example value |
|---|---|---|
| A | Which IPv4 address serves this name | 203.0.113.10 |
| AAAA | Which IPv6 address serves this name | 2001:db8::1 |
| CNAME | This name is an alias for another name | target.example.net. |
| MX | Which servers accept mail for this domain | 10 mail.example.com. |
| TXT | Arbitrary text, used for verification and policy | v=spf1 include:_spf.google.com ~all |
| NS | Which nameservers are authoritative for this zone | ns1.example-dns.com. |
| PTR | Which name belongs to this IP address | mail.example.com. |
| CAA | Which authorities may issue certificates | 0 issue "letsencrypt.org" |
| SOA | Administrative metadata for the zone | ns1.example.com. admin.example.com. … |
A and AAAA: the address records
A and AAAA are the same idea in two address families. An A record points a hostname at an IPv4 address; AAAA points it at an IPv6 address. A name can carry several of each, and resolvers will hand out different ones — that is the simplest form of load distribution DNS offers.
Publishing only A is entirely normal and costs nothing in search. IPv6 is optional, and crawlers reach IPv4-only hosts without difficulty.
example.com. 3600 IN A 203.0.113.10
example.com. 3600 IN AAAA 2001:db8::1
www.example.com. 3600 IN A 203.0.113.10
; name TTL class type value
; The trailing dot matters: it marks a fully
; qualified name. Without it, the zone's own
; domain is appended.CNAME: an alias, with one hard rule
A CNAME says "this name is really that name" — the resolver restarts its lookup at the target. It is the right choice for pointing a subdomain at a service whose address you do not control and should not hardcode.
The rule people hit is that a name with a CNAME may hold no other records. That makes a CNAME impossible at the zone apex, because the apex must carry NS and SOA. Providers work around this with ALIAS or ANAME records, which behave like a CNAME but resolve server-side and so leave the apex free of the conflict.
; Fine — a subdomain aliasing a service
shop.example.com. 3600 IN CNAME shops.myprovider.net.
; Invalid — the apex already needs NS and SOA
example.com. 3600 IN CNAME target.example.net.
; The workaround most providers offer
example.com. 3600 IN ALIAS target.example.net.MX and TXT: mail and everything else
MX records name the servers that accept mail for a domain, each with a preference number where lower wins. The number is a priority, not a weight — the second entry is a fallback, not a share of the traffic.
TXT is the catch-all. It carries no fixed meaning, which is exactly why it ended up hosting domain verification, SPF, DKIM and DMARC. The type does not validate the content: a malformed SPF record is a perfectly valid TXT record, which is why these fail silently.
example.com. 3600 IN MX 10 mail1.example.com.
example.com. 3600 IN MX 20 mail2.example.com.
; SPF lives in a TXT record at the apex
example.com. 3600 IN TXT "v=spf1 include:_spf.google.com ~all"
; DMARC lives on its own subdomain
_dmarc.example.com. 3600 IN TXT "v=DMARC1; p=none; rua=mailto:d@example.com"The types you meet less often
The one worth adding deliberately is CAA: it takes one line and removes a whole class of misissuance risk. To see what a domain currently publishes, run it through the DNS checker .
- NS delegates a zone to its authoritative nameservers. Change these and you have moved the whole zone.
- PTR maps an IP back to a name. It lives in the reverse zone, which your hosting provider usually controls rather than you.
- CAA lists which certificate authorities may issue for the domain — a cheap way to stop misissuance.
- SOA holds the zone's serial number and timing values, including the negative-caching TTL that decides how long a "does not exist" answer sticks.
- SRV points at a service on a specific host and port, used by autodiscover and similar protocols.
How DomainLens contributes
DomainLens reports the records a domain publishes as part of every audit, so a missing address record or absent mail authentication shows up beside the on-page findings. For why a change has not taken effect yet see DNS propagation , for the alias question see CNAME vs A record , and for the mail records see SPF, DKIM and DMARC .
- What is the difference between an A record and a CNAME?
- An A record points a name at an IP address directly. A CNAME points a name at another name, and the resolver looks that up in turn. Use A when you control the address, CNAME when you point at a service that manages its own.
- Why can I not put a CNAME on my root domain?
- Because a name with a CNAME may hold no other records, and the root must carry NS and SOA. Providers offer ALIAS or ANAME records that achieve the same result without the conflict.
- Do DNS records affect SEO directly?
- Only in the sense that a name which does not resolve cannot be crawled at all. Beyond reachability, Google does not read your zone as a ranking input.
- How many TXT records can a domain have?
- As many as you like, and multiple TXT records at one name are normal. The exception is SPF: exactly one SPF record is allowed, and publishing two invalidates both.