The DNS AAAA record (pronounced "quad-A record") maps a domain name to an IPv6 address. As the internet transitions from the 32-bit IPv4 address space to the vastly larger 128-bit IPv6 space, AAAA records are becoming as essential as their A record counterparts for any internet-facing service.
What Is an AAAA Record?
An AAAA record works exactly like an A record, but instead of returning a four-octet IPv4 address, it returns a 128-bit IPv6 address written in colon-separated hexadecimal notation. The name "quad-A" comes from the fact that IPv6 addresses are four times as long (128 bits) as IPv4 addresses (32 bits).
When a client that supports IPv6 queries DNS for a domain, the resolver returns the AAAA record. If both A and AAAA records are present, modern operating systems and browsers prefer IPv6 by default through a mechanism described in RFC 6724 — a process often called "Happy Eyeballs" (RFC 8305), where both are tried in parallel and the fastest connection wins.
IPv6 Address Format
IPv6 addresses consist of eight groups of four hexadecimal digits, separated by colons. Leading zeros in each group can be omitted, and one or more consecutive groups of all zeros can be replaced with a double colon (::) — but this shorthand can only appear once in an address.
; Full IPv6 address
2001:0db8:0000:0000:0000:0000:0000:0001
; With leading zeros removed
2001:db8:0:0:0:0:0:1
; With consecutive zero groups collapsed (:: shorthand)
2001:db8::1AAAA Record Syntax
AAAA records follow the same zone file format as A records. The only differences are the record type field and the address format in the RDATA column.
; AAAA record syntax
; NAME TTL CLASS TYPE RDATA (IPv6 address)
example.com. 3600 IN AAAA 2001:db8::1
www.example.com. 3600 IN AAAA 2001:db8::1
; Subdomain pointing to a different IPv6 address
mail.example.com. 3600 IN AAAA 2001:db8:cafe::25Why IPv6 Matters
The IPv4 address pool is effectively exhausted. Regional Internet Registries (RIRs) ran out of new allocations years ago, and organizations now acquire IPv4 addresses on secondary markets at significant cost. IPv6, with its 340 undecillion (3.4 × 1038) possible addresses, solves this scarcity problem permanently.
Beyond addressing, IPv6 offers other advantages: simplified routing through hierarchical address allocation, built-in support for stateless address autoconfiguration (SLAAC), mandatory IPsec support in the protocol specification, and improved multicast capabilities. Mobile networks and cloud providers have aggressively adopted IPv6, meaning a growing fraction of your visitors likely connect over IPv6.
Dual-Stack: Running A and AAAA Records Together
The recommended approach for any public-facing service is to publish both an A record and an AAAA record for the same domain name — a configuration called dual-stack. IPv6-capable clients will connect over IPv6; legacy IPv4-only clients will use the A record. No traffic is lost in either direction.
; Dual-stack configuration: A record + AAAA record for the same domain
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
www.example.com. 3600 IN AAAA 2001:db8::1A Record vs. AAAA Record Comparison
| Feature | A Record | AAAA Record |
|---|---|---|
| Address family | IPv4 | IPv6 |
| Address length | 32 bits | 128 bits |
| Example address | 203.0.113.10 | 2001:db8::1 |
| DNS record type | A (type 1) | AAAA (type 28) |
| Client preference | Fallback when IPv6 unavailable | Preferred by modern clients |
| Can coexist at apex | Yes | Yes |
How to Check a AAAA Record
You can look up any domain's AAAA record using the ShowDNS DNS Lookup tool. Select the AAAA record type, enter the domain, and the tool will return the current IPv6 address and TTL as reported by the authoritative nameservers.
On the command line, use dig with the AAAA type:
; Query AAAA record with dig
dig example.com AAAA
;; ANSWER SECTION:
example.com. 3600 IN AAAA 2606:2800:220:1:248:1893:25c8:1946Frequently Asked Questions
Do I need a AAAA record if I already have an A record?
You don't strictly need one, but it is strongly recommended. Without a AAAA record, IPv6-only clients cannot reach your domain. As IPv6 adoption grows — especially on mobile networks — omitting a AAAA record increasingly means missing a portion of your audience. Adding one is free and has no downside as long as your server is configured to listen on the IPv6 address.
What happens if my AAAA record points to an unreachable address?
IPv6-capable clients will attempt to connect to the IPv6 address first. If the connection times out, most modern clients will fall back to the A record, but this fallback adds several seconds of latency. To avoid this degraded experience, only publish a AAAA record when the IPv6 address is fully operational and reachable.
Can I use AAAA records for email (MX)?
Yes — but with caveats. The MX record points to a hostname, not an IP address directly. That hostname can have both A and AAAA records, and mail servers that support IPv6 will use the AAAA record. However, not all mail servers support IPv6, and some spam filtering systems treat IPv6-sourced mail with extra scrutiny. Check your mail provider's documentation before enabling IPv6 for mail delivery.
Why is it called a "quad-A" record?
The name reflects the address size ratio. An IPv4 address is 32 bits, and the A record holds it. IPv6 addresses are 128 bits — four times as long (4 × 32 = 128). So the record type is AAAA: four As for four times the bits. It is DNS record type number 28 in the IANA registry.
How do I get an IPv6 address for my server?
Most modern cloud providers (AWS, Google Cloud, DigitalOcean, Vultr, Linode) automatically assign an IPv6 address to new servers or let you enable it with a single click. For dedicated or co-located servers, contact your hosting provider or upstream ISP to request an IPv6 allocation. Once you have the address, configure it on your server's network interface and add the AAAA record in your DNS control panel.