What it's for
An AAAA record is the IPv6 counterpart to an A record — it maps a hostname to a 128-bit IPv6 address instead of a 32-bit IPv4 one. The name is a small joke: IPv6 addresses are four times the size of IPv4 addresses, so the record type is "four A's" — AAAA.
As IPv4 address space has run out and IPv6 adoption has grown (a large and increasing share of global internet traffic — mobile carriers in particular — now runs over IPv6), having an AAAA record alongside your A record is no longer optional for anyone who wants full performance and reachability. Clients on IPv6-only or IPv6-preferring networks will use the AAAA record when it's available and only fall back to IPv4 (via the A record) when it isn't.
Format & syntax
example.com. 3600 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
- Name — the hostname
- TTL — cache duration in seconds
- Class —
IN - Type —
AAAA - Value — a valid IPv6 address, written in the standard colon-hex notation. Leading zeros in each group can be omitted, and one run of consecutive all-zero groups can be collapsed to
::(only once per address).
Like A records, a hostname can have multiple AAAA records for load distribution across IPv6 endpoints.
How it's used in practice
- Dual-stack hosting — the standard modern setup: an A record and an AAAA record for the same hostname, so clients connect over whichever protocol they support, with IPv6 generally preferred when available.
- CDN and cloud provider defaults — most major CDNs (Cloudflare, Fastly, CloudFront) and cloud load balancers provision AAAA records automatically once IPv6 is enabled on a service, so this is often more "flip a setting" than "manually write records."
- IPv6-only infrastructure — increasingly common inside container orchestration and internal service meshes, where IPv4 address exhaustion inside large private networks (yes, even RFC 1918 space runs out at scale) pushes teams toward IPv6-only internal DNS.
- Testing and validation — developers deliberately query AAAA records to confirm a service is reachable over IPv6 before flipping DNS over publicly, since IPv6 connectivity bugs (broken routing, misconfigured firewalls) are easy to miss if you only ever test over IPv4.
Common mistakes & gotchas
- Publishing a broken AAAA record — this is the classic "IPv6 brownout" bug: you add an AAAA record pointing at a host that doesn't actually have working IPv6 connectivity (firewall blocking it, misconfigured routing), and IPv6-preferring clients silently fail or fall back slowly instead of just using IPv4. Only publish an AAAA record once you've verified the IPv6 path actually works end to end.
- Forgetting AAAA when copying an A record setup — teams that manually manage zone files often update the A record during a migration and forget the AAAA record entirely, leaving the IPv6 path pointed at a dead or old server.
- Assuming IPv6 isn't relevant to your traffic — a meaningful and growing share of mobile and residential traffic is IPv6-primary. Skipping AAAA doesn't break anything (fallback to A still works) but it does mean missing out on IPv6's benefits and, in some cases, slower connection setup as clients try IPv6 first and time out before falling back.
- Address notation mistakes — IPv6 addresses are long and easy to mistype. Double-colon compression (
::) can only be used once per address; using it twice makes the address ambiguous and invalid.
Comparison & FAQ
| Type | Purpose | Key difference from AAAA |
|---|---|---|
| A | Maps a hostname to an IPv4 address | Same job, IPv4 instead of IPv6 |
| CNAME | Aliases a hostname to another hostname | Points to a name, not an address |
| PTR | Maps an IP address back to a hostname | The reverse operation, works for IPv6 too (under ip6.arpa) |
Do I need an AAAA record if I already have an A record?
Not strictly — IPv4 traffic will still work fine. But without an AAAA record you're invisible to clients that prefer or require IPv6, and you lose out on the (often measurable) performance benefits IPv6 can bring on modern networks.
What happens if my AAAA record points to a broken IPv6 endpoint?
Clients that prefer IPv6 will try to connect over IPv6 first, fail or time out, and then fall back to IPv4 — but that fallback isn't instant, so users on IPv6-preferring networks can see noticeably slower page loads. This is why you should only publish AAAA once IPv6 connectivity is verified working.
How is an IPv6 address different from IPv4 in an AAAA record?
IPv6 addresses are 128 bits, written as eight groups of four hex digits separated by colons, versus IPv4's 32 bits written as four decimal octets. IPv6 also supports :: shorthand to compress one run of consecutive zero groups.
Can I have multiple AAAA records for one hostname?
Yes, the same way you can have multiple A records — a resolver returns all of them and the client or resolver picks one, giving you basic DNS-level load distribution over IPv6.