What Is an AAAA Record?
An AAAA record (also called a "quad-A" record) is a DNS record that maps a domain name to an IPv6 address. It is the IPv6 equivalent of the A record, which maps to IPv4 addresses.
How AAAA Records Work
When a client needs to connect to a domain over IPv6, the DNS resolver queries for AAAA records. The authoritative nameserver returns the 128-bit IPv6 address (e.g., 2606:2800:220:1:248:1893:25c8:1946). The client then connects using that address.
The name "AAAA" reflects that IPv6 addresses are 128 bits — four times the 32-bit size of IPv4 addresses stored in A records. Most modern operating systems and browsers prefer IPv6 when available, using the "Happy Eyeballs" algorithm to choose the fastest connection.
AAAA Records and Dual-Stack Configuration
Best practice is to publish both A and AAAA records for your domain (dual-stack). This ensures compatibility with IPv4-only clients while supporting IPv6 connections. As IPv6 adoption grows, having AAAA records becomes increasingly important for accessibility.
AAAA Records and Email
If your mail server supports IPv6, you should add AAAA records to the hostnames referenced in your MX records. Major email providers like Gmail and Outlook support IPv6 SMTP delivery. When adding IPv6 to your mail infrastructure, remember to update your SPF record with ip6: mechanisms to include your IPv6 addresses.
Frequently Asked Questions
What is the difference between an A record and an AAAA record?
An A record maps a domain to a 32-bit IPv4 address. An AAAA record maps to a 128-bit IPv6 address. Both serve the same purpose — domain name to IP address resolution — but for different IP versions.
Do I need AAAA records for email?
If your mail server has IPv6 connectivity, AAAA records on your MX hosts enable IPv6 email delivery. Ensure your SPF record includes the IPv6 addresses to prevent authentication failures.
Can I have both A and AAAA records for the same domain?
Yes. This dual-stack approach is recommended. IPv6-capable clients use the AAAA record, while IPv4-only clients fall back to the A record automatically.