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AAAA record

An AAAA record is a DNS record that stores an IPv6 address for a domain name or host name. IPv6 is the newer version of the Internet Protocol, and its addresses are longer than IPv4 addresses. When software asks DNS for a name's AAAA record, the answer can tell a device or program that supports IPv6 which address to contact.

What does an AAAA record look like?

An IPv6 address is written using groups of hexadecimal numbers (using digits and the letters a to f) separated by colons. For example, 2001:db8::25 is a documentation-only address that could appear in an illustrative AAAA record for www.example.com. The record associates the name with that IPv6 address; DNS does not test whether a service at the address is available.

If a server has multiple IPv6 addresses that should be found for the same name, DNS can return multiple AAAA records. A site may also have an A record for IPv4, so clients on networks using different IP versions can find an address. The address version used to connect to DNS itself does not determine whether the answer contains IPv4 or IPv6 data.

How is AAAA different from A?

An A record contains an IPv4 address, typically shown as four decimal numbers separated by dots. An AAAA record contains a 128-bit IPv6 address, typically shown in hexadecimal groups separated by colons. The names “A” and “AAAA” identify different DNS record types; the record type itself does not guarantee that a visitor's network supports that version of IP.

For example, if www.example.com has both A and AAAA records, a browser may use IPv6 when the user's network and connection support it, or IPv4 otherwise. The owner still needs the web service reachable at the published addresses. An outdated AAAA record can cause connection problems for some IPv6 users even when the A record is correct.

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