An AAAA record maps a hostname to an IPv6 address. It is the IPv6 counterpart of an A record: same role, different address space. When a hostname publishes both, clients on dual-stack networks usually prefer IPv6 and fall back to IPv4 only if the IPv6 connection fails. The name reflects the size: an IPv6 address is four times longer than an IPv4 address.
Why it matters
A growing share of mobile networks and ISPs now route traffic over IPv6 by default. Without an AAAA record, those clients are forced through carrier-grade NAT or translation, adding latency and connection failures that show up as flaky uptime and slow page loads. Publishing an AAAA is also part of several public-sector compliance baselines.
How to check
- Confirm your hosting provider, load balancer, and firewall accept IPv6 traffic before adding the record.
- Run
dig +short example.com AAAAand verify the address belongs to the right server or CDN edge. - Keep A and
AAAArecords aligned to the same logical service. - Use the same TTL on both records so failover behaves predictably.
- For platform-hosted subdomains, prefer a CNAME so the provider manages both stacks.
- Test from an IPv6-only client or
curl -6to confirm end-to-end reachability, not just resolution.