How does an AAAA record differ from an A record?

An A record points to a 32‑bit IPv4 address (for example 192.0.2.1); an AAAA record points to a 128‑bit IPv6 address (for example 2001:db8::1). Same purpose — name to address — different address family.

Do I need both an A and an AAAA record?

If your server supports IPv6, publish both. Clients on IPv4 use the A record and clients on IPv6 use the AAAA record, so serving both reaches everyone. If your host has no IPv6 address, don't publish an AAAA record at all — an AAAA pointing at an unreachable address will strand IPv6 visitors.

What TTL should I use for an AAAA record?

3600 seconds (one hour) is a reasonable default. Drop it to 300 seconds before a planned change so updates propagate quickly, then raise it again once the address is settled.

Can an AAAA record cause email to fail?

Indirectly, yes. If you send mail over IPv6, receivers expect the sending host's AAAA and reverse PTR records to match and your SPF to cover the IPv6 source. A missing PTR or an IPv6 range absent from SPF is a common cause of IPv6‑only delivery problems.

Why is my AAAA record not resolving?

The usual causes are propagation delay right after a change, a typo in the shortened :: notation, or an AAAA record on a host that isn't actually reachable over IPv6. Query it with dig AAAA yourdomain.com to see what authoritative DNS is returning, and confirm the host answers with ping -6.

What is an AAAA DNS record (Quad‑A explained)?

An AAAA record — spoken as "Quad‑A" — is the DNS record that maps a domain name to an IPv6 address. It does the same job as an A record, which maps a domain to an IPv4 address, but for the newer and much larger IPv6 address space.

The difference is the address family it points at. An A record holds a 32‑bit IPv4 address — four decimal groups separated by dots, like 192.0.2.1. An AAAA record holds a 128‑bit IPv6 address — eight groups of four hexadecimal digits separated by colons, like 2001:db8:85a3::8a2e:370:7334. IPv6's larger word size is also where the name comes from: an IPv6 address is four times the length of an IPv4 one, hence four "A"s.

Why IPv6 exists

IPv4 can represent only about 4.3 billion unique addresses, and in most regions that pool has already been exhausted. IPv6 expands the space to roughly 340 undecillion (3.4 × 10³⁸) addresses — enough to end the scarcity that forced workarounds like Network Address Translation (NAT).

Beyond raw scale, IPv6 simplified the packet header for more efficient routing and replaced broadcast with more targeted multicast and neighbor‑discovery mechanisms. It was also designed with IPsec in mind, though — contrary to a common myth — IPsec is not automatically switched on just because a host uses IPv6; it still has to be configured.

How the AAAA record fits with other DNS records

An AAAA record is one of a handful of record types a domain typically publishes. The common ones:

A record — maps a domain to an IPv4 address.
AAAA record — maps a domain to an IPv6 address (the subject of this guide).
CNAME record — aliases one name to another, useful for subdomains like www or mail.
MX record — names the mail servers that receive email for the domain.
TXT record — holds arbitrary text, and is where email‑authentication records such as SPF and DMARC live.

When a visitor's network supports IPv6 and your domain has an AAAA record, the resolver returns the IPv6 address and the client connects over IPv6. If only an A record exists, the client falls back to IPv4. Publishing both lets clients on either protocol reach you.

How to add an AAAA record

Confirm IPv6 support. Check that your hosting or server environment actually has a routable IPv6 address — many do not by default.
Get the IPv6 address. Obtain it from your host or ISP. It will be a full 128‑bit address, often written in the shortened :: form.
Open your DNS editor. Log in to the registrar or DNS provider that manages your zone.
Create the record. Choose type AAAA, set the Host/Name (@ for the root domain, or www, mail, etc.), and paste the IPv6 address as the value.
Set a TTL. A shorter time‑to‑live (for example 300 seconds) is handy while you're testing; a longer one (3600 seconds) is fine once the address is stable.
Save and let it propagate. Changes are usually visible within minutes but can take up to 48 hours to reach every resolver, depending on prior caching.

How to test an AAAA record

Query the record directly instead of waiting on propagation:

On any platform: dig AAAA yourdomain.com (or nslookup -type=AAAA yourdomain.com on Windows) returns the published IPv6 address.
A hosted DNS lookup tool does the same from the browser and checks multiple resolvers at once.
To confirm the host actually answers over IPv6, ping -6 yourdomain.com verifies end‑to‑end connectivity.

AAAA records and email authentication

If any of your mail leaves the building over IPv6, DNS accuracy stops being cosmetic. Receivers like Gmail apply stricter checks to IPv6 senders: mail from an IPv6 address is expected to have valid forward and reverse DNS (a matching PTR record) and to pass SPF or DKIM with DMARC alignment. A missing or mismatched AAAA/PTR pair on a sending host is a fast way to land in spam. If you configure SPF, DKIM, and DMARC, make sure your SPF record authorizes the IPv6 ranges you actually send from, not just IPv4.

Best practices

Publish A and AAAA together when your server is dual‑stack, so no client is left out.
Audit records regularly — a stale AAAA pointing at a decommissioned address causes intermittent, hard‑to‑diagnose failures for IPv6 users only.
Enable DNSSEC to protect resolvers from forged answers.
Keep TTLs sensible — short while changing, longer once stable.