Glossary

AAAA Record

Maps a domain name to an IPv6 address

An AAAA record (pronounced "quad-A record") is a DNS record type that maps a domain name to a 128-bit IPv6 address, the modern successor to IPv4, enabling connectivity on next-generation networks.

What is an AAAA Record?

An AAAA record serves the same fundamental purpose as an A record — translating a human-readable domain name into a machine-readable IP address — but it does so for IPv6 rather than IPv4. IPv6 addresses are 128 bits long and written in hexadecimal notation, such as 2606:2800:220:1:248:1893:25c8:1946. The name "quad-A" (AAAA) reflects the fact that IPv6 addresses are four times the size of IPv4 addresses.

IPv6 was introduced to solve the exhaustion of the IPv4 address space. With only around 4.3 billion possible IPv4 addresses, the internet ran out of unallocated blocks years ago. IPv6 provides approximately 340 undecillion unique addresses, more than enough to assign one to every device on Earth for the foreseeable future.

Most modern domains publish both A and AAAA records so they can be reached over both IPv4 and IPv6. Clients that support IPv6 will typically prefer the AAAA record, while older or IPv4-only clients fall back to the A record.

How Does an AAAA Record Work?

The resolution process for an AAAA record is identical to that of an A record. When a DNS resolver receives a query for a domain, it can request either an A record (IPv4) or an AAAA record (IPv6) depending on the client's capabilities. Most modern operating systems perform dual-stack lookups, requesting both record types simultaneously and using whichever address type the network prefers, usually according to the Happy Eyeballs algorithm (RFC 6555).

If a domain has an AAAA record and the client is on an IPv6-capable network, the connection will be established over IPv6. This offers benefits including a larger address space, built-in support for IPsec, more efficient routing, and elimination of NAT in many cases. If the AAAA lookup fails or the network does not support IPv6, the client gracefully falls back to the A record and IPv4.

Configuring AAAA records is done through your DNS provider using the same interface as A records, simply selecting AAAA as the record type and entering the IPv6 address.

How to Check an AAAA Record

To verify the AAAA record for any domain, use the AAAA Record Lookup tool at nslookup.net/tools/aaaa-record-lookup. Enter the domain name and the tool will query authoritative DNS servers and return all AAAA records along with their TTL values. This is helpful when setting up IPv6 for the first time, troubleshooting dual-stack connectivity, or confirming that a CDN or hosting provider has published the correct IPv6 address.

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AAAA Record Lookup

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Frequently Asked Questions

Do I need an AAAA record if I already have an A record?

You do not strictly need an AAAA record to have a functioning website, as IPv4 still works fine. However, publishing an AAAA record is increasingly recommended because a growing portion of internet traffic travels over IPv6, and some networks (especially mobile carriers) are IPv6-first. Adding an AAAA record future-proofs your domain and ensures compatibility with all users.

Why is it called a "quad-A" record?

The name comes from the relationship between IPv4 and IPv6 address sizes. An IPv4 address is 32 bits, and an IPv6 address is 128 bits — exactly four times larger. Since the IPv4 record is called an "A" record (one A), the IPv6 record is called an "AAAA" record (four As). It is a somewhat informal but widely accepted naming convention.

Can a domain have both an A record and an AAAA record?

Yes, and this is considered best practice. Publishing both records allows a domain to be reached over either IPv4 or IPv6. Modern clients use a dual-stack approach and will select the most appropriate protocol based on network conditions. This is transparent to end users and improves overall reachability.

What does an IPv6 address look like in an AAAA record?

An IPv6 address consists of eight groups of four hexadecimal digits separated by colons, for example 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Leading zeros within each group can be omitted, and one consecutive sequence of all-zero groups can be replaced with a double colon (::), so the same address might appear as 2001:db8:85a3::8a2e:370:7334.