Guide
Understanding the DNS AAAA Record: How Domains Resolve Over IPv6
Written By Nadeem Khan, WhoisFreaks Team Published: July 20, 2026, Last Updated: July 20, 2026
Guide
Written By Nadeem Khan, WhoisFreaks Team Published: July 20, 2026, Last Updated: July 20, 2026
A DNS AAAA record maps a domain name to an IPv6 address, the same job an A record does for IPv4. When a visitor reaches your site from an IPv6 network, the AAAA record is what tells their device which numeric address to connect to. If the A record is the entry that carried the web through its first few decades, the AAAA record is the one carrying it into the IPv6 era.
This section builds on the A record you read about earlier and assumes you already know the basics of the Domain Name System (DNS). Below you will find what an AAAA record is, how it differs from an A record, how it behaves during resolution, and how to check one yourself.
Quick answer: An AAAA record (spoken as "quad-A") is a DNS record that stores a single 128-bit IPv6 address for a host. It works exactly like an A record, except it points to an IPv6 address instead of an IPv4 one. A domain can hold both, so it stays reachable over either protocol.
The AAAA record was first defined in RFC 1886 in December 1995, when IPv6 was still early in its life. The current specification, RFC 3596, replaced it in October 2003 and folded in a later change that moved IPv6 reverse lookups to the IP6.ARPA domain. An earlier alternative design that split addresses across multiple records was tried and then abandoned, and RFC 3596 has been the settled standard ever since.
That history matters for one practical reason: AAAA is old, stable, and universally supported. Any resolver or DNS host you touch today already knows how to handle it.
An AAAA record is a resource record that stores one IPv6 address for a hostname. Per RFC 3596, it belongs to the Internet class, carries the IANA-assigned type number 28, and holds a 128-bit address in its data field. When a client asks DNS for the AAAA record of a domain, it gets back every IPv6 address published for that name.
The four A's are usually explained as a nod to size. An IPv4 address is 32 bits and lives in an A record. An IPv6 address is 128 bits, four times as long, so the record that holds it picked up four A's. The naming is informal, but it is a useful way to remember which record carries the larger address.
Both records answer the same question, "what address does this name point to," but for different protocol versions. The short version:
| A record | AAAA record | |
|---|---|---|
| Address type | IPv4 | IPv6 |
| Address size | 32-bit | 128-bit |
| Example value | 192.0.2.1 | 2001:db8::1 |
| DNS type number | 1 | 28 |
| Notation | Dotted decimal | Colon-separated hextets |
A domain does not choose one or the other. It is normal to publish an A record and an AAAA record for the same name so that IPv4 clients and IPv6 clients can both connect. For the full treatment of the IPv4 side, see the DNS A record section.
When you open a website, your device asks a resolver for the addresses behind the domain. On a dual-stack connection, meaning one that supports both IPv4 and IPv6, the resolver can return both the A and AAAA records. The device then decides which to use.
Modern clients do not simply prefer one protocol and wait. They try IPv6 and IPv4 connections almost in parallel and keep whichever one completes first, a behavior known as Happy Eyeballs. The effect for a user is that a slow or broken IPv6 path does not stall the page, it just falls back to IPv4 quietly. For a refresher on how a query travels from client to authoritative server, see DNS resolution.
In a zone file, an AAAA record follows the same shape as an A record, with AAAA as the type and an IPv6 address as the value. A typical AAAA record example looks like this:
example.com. 3600 IN AAAA 2001:db8::1
www.example.com. 3600 IN AAAA 2001:db8::2Each line sets the hostname, the TTL in seconds, the class (IN for Internet), the record type (AAAA), and the IPv6 address. TTL choices work the same as they do for A records: shorter values (300 to 900 seconds) give you faster changes during a migration, longer values (3600 seconds and up) cut lookups and add stability. IPv6 addresses can be written in shortened form, so 2001:0db8:0000:0000:0000:0000:0000:0001 and 2001:db8::1 are the same address.
The main use is making a service reachable over IPv6: a website, an API endpoint, or a mail server all become IPv6-accessible once an AAAA record points at an IPv6-capable host. Beyond that, AAAA records support the same patterns as A records. You can publish several AAAA records for one name to spread traffic across servers, and different hostnames can point to the same IPv6 address. As more networks turn on IPv6 by default, publishing an AAAA record next to your A record is the practical way to stay fast and reachable for every visitor.
Publishing more than one AAAA record for the same hostname is the simplest way to spread traffic across multiple IPv6 servers. RFC 3596 allows a host with several IPv6 addresses to hold several AAAA records, and most authoritative servers hand back that set in a rotating order, a technique called DNS round-robin. Different clients receive the addresses in different orders, connect to whichever comes first, and the load ends up spread across the servers.
It is a blunt instrument, though, and worth understanding before you lean on it. DNS caching means a resolver can hold one ordering for the length of the TTL, so the split is approximate rather than even. There is no health checking either: DNS keeps handing out the address of a server that has gone down until you remove the record yourself. Client-side address selection can skew things further, since a device may reorder the candidate addresses by its own rules instead of using the first one returned.
For traffic that needs real balancing with health awareness, a dedicated load balancer or an anycast setup is the stronger choice. There, the AAAA record usually points at a single front-end address and the balancing happens behind it. Round-robin AAAA records are best kept for lightweight distribution and redundancy where the occasional imbalance is acceptable.
IPv6 addresses are longer than IPv4 addresses, so responses that carry several AAAA records, or AAAA records alongside signed DNSSEC data, can grow past the old 512-byte limit for a basic UDP DNS reply. DNS handles this with an extension that lets a resolver advertise support for larger UDP responses. When a reply is still too large, the server sets a truncation flag and the resolver retries over TCP. In day-to-day use this is automatic, but it is worth knowing when you debug missing answers on networks that block large UDP packets or TCP port 53.
The fastest way to run an AAAA record lookup is the WhoisFreaks DNS lookup tool. Enter the domain, choose the AAAA type, and read the parsed IPv6 addresses back in JSON, XML, or raw output. It is the same workflow shown for A records earlier in this guide, with the record type switched to AAAA.
On your own machine, dig and nslookup both query AAAA records:
dig example.com AAAA
dig +short example.com AAAA
nslookup -type=AAAA example.comdig +short returns just the addresses, which is handy in scripts. dig also shows the TTL and the answering server, useful when you are checking whether a change has propagated.
For monitoring many domains or auditing IPv6 coverage across a portfolio, checking records by hand does not scale. The WhoisFreaks DNS API returns parsed AAAA data programmatically, so you can pull IPv6 records for thousands of hosts and flag the ones missing an AAAA entry. The same dig +short example.com AAAA call also works well inside a shell loop for smaller batches.
"AAAA record not found." This usually means the domain has no IPv6 address published, not that something is broken. Plenty of domains still run IPv4-only with just an A record. Confirm whether an AAAA record is actually expected before treating it as an error.
IPv6 not being used even though an AAAA record exists. The client or its network may not have working IPv6, so it falls back to the A record. That is the system behaving as designed.
Broken IPv6 and withheld AAAA records (advanced). Some operators deliberately hold back AAAA records when a segment of their IPv6 path is unreliable, because a broken IPv6 route can slow the first connection attempt for affected users. If you are debugging inconsistent behavior, dig +trace example.com AAAA helps you see whether the authoritative server is the one returning the record and separates a publishing problem from a local network one.
The AAAA record is the IPv6 half of how DNS points names at machines. It works like the A record you already know, stores a 128-bit address instead of a 32-bit one, and coexists with A records so a domain answers to both protocols. Publish both, verify them, and IPv6 stops being something you worry about and becomes something that just works. When you need to check IPv6 coverage across many domains at once, the DNS API shown above turns that from a manual chore into a single query. And to go the other direction, from an IPv6 address back to the domains sitting behind it, the WhoisFreaks reverse DNS lookup tool resolves the reverse side of your AAAA records.