DNS AAAA Record Explained: IPv6 Addresses

An AAAA record (pronounced "quad-A") maps a domain name to an IPv6 address. It does the same job as an A record, but for the newer, longer IP address format. If your server has an IPv6 address and you want users on IPv6 networks to reach it, you need an AAAA record.

IPv6 adoption has been growing steadily. Google reports that over 45% of users accessing their services do so over IPv6. Major mobile carriers route most traffic over IPv6 by default. If your domain only has A records pointing to IPv4 addresses, a significant chunk of your users may be going through translation layers that add latency. For a broader overview of all DNS record types, see DNS Record Types Explained.

What an AAAA Record Looks Like

An AAAA record contains the domain name, a TTL value, the record class, the record type, and an IPv6 address.

example.com.    3600    IN    AAAA    2001:0db8:85a3:0000:0000:8a2e:0370:7334

Breaking this down:

• example.com. is the domain name (with trailing dot indicating the root)
• 3600 is the TTL in seconds (1 hour)
• IN is the class (Internet)
• AAAA is the record type
• 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is the IPv6 address

IPv6 addresses are 128-bit numbers written as eight groups of four hexadecimal digits, separated by colons. They are much longer than IPv4 addresses, which is why they get their own record type rather than sharing the A record.

IPv6 addresses can be shortened by dropping leading zeros and collapsing consecutive groups of all-zeros with :::

# Full form
2001:0db8:85a3:0000:0000:8a2e:0370:7334

# Shortened form
2001:db8:85a3::8a2e:370:7334

Both represent the same address. DNS providers typically accept either format when you create the record.

IPv4 vs IPv6: Why Two Record Types

IPv4 uses 32-bit addresses (like 93.184.216.34), giving roughly 4.3 billion unique addresses. That sounded like plenty in the 1980s, but the internet outgrew it. IPv4 address exhaustion has been a real problem since the early 2010s, with regional internet registries running out of fresh blocks to allocate.

IPv6 uses 128-bit addresses, providing 340 undecillion unique addresses. That is 340 followed by 36 zeros. Enough for every device on the planet to have billions of addresses each.

The A record was defined in RFC 1035 back in 1987. The AAAA record was defined later in RFC 3596 (2003), specifically to handle the longer IPv6 address format [1]. The name "AAAA" comes from the fact that an IPv6 address is four times the length of an IPv4 address (128 bits vs 32 bits), so it takes four "A"s.

When You Need AAAA Records

Not every domain needs AAAA records today, but the reasons to add them keep growing.

Your Hosting Provider Supports IPv6

If your web server, CDN, or cloud provider has assigned an IPv6 address to your service, create an AAAA record pointing to it. Most major providers now support IPv6: AWS, Google Cloud, Azure, Cloudflare, DigitalOcean, and others all offer IPv6 addresses.

You Want Better Mobile Performance

Mobile carriers have been aggressive about IPv6 adoption because they face the most acute IPv4 address shortage. T-Mobile in the US routes over 90% of its traffic over IPv6. Verizon and AT&T are similar. When a mobile user on an IPv6-only network tries to reach your IPv4-only site, their carrier has to translate the traffic through NAT64 or similar mechanisms. That translation adds latency and introduces a potential point of failure.

With an AAAA record, IPv6 users connect directly. No translation needed.

You Are Running a Dual-Stack Network

Dual-stack means your server has both an IPv4 and an IPv6 address. In this configuration, you publish both an A record and an AAAA record. Clients that support IPv6 use the AAAA record; clients on IPv4 use the A record. Everyone gets a direct connection.

Future-Proofing

IPv4 addresses are a finite, increasingly expensive resource. IPv6 is the long-term direction of the internet. Adding AAAA records now ensures your domain works well as IPv6 adoption continues to grow.

How to Check AAAA Records

You can query AAAA records using standard DNS tools.

Using dig

dig example.com AAAA

The output shows the AAAA record in the answer section:

;; ANSWER SECTION:
example.com.        3600    IN    AAAA    2606:2800:21f:cb07:6820:80da:af6b:8b2c

If no AAAA record exists, the answer section will be empty.

To check both A and AAAA records together:

dig example.com A
dig example.com AAAA

Or query for ANY records (though some resolvers no longer support ANY queries fully):

dig example.com ANY

Using nslookup

nslookup -type=AAAA example.com

Using Online Tools

If you do not have command-line access, online DNS lookup tools like the one on How to Check DNS Records let you query any record type from a browser.

How to Create an AAAA Record

The process depends on your DNS provider, but the general steps are the same.

dig yourdomain.com AAAA

Example: Root Domain and WWW Subdomain

A typical dual-stack setup for a website includes both A and AAAA records for the root domain and the www subdomain:

example.com.      3600    IN    A       93.184.216.34
example.com.      3600    IN    AAAA    2606:2800:21f:cb07:6820:80da:af6b:8b2c
www.example.com.  3600    IN    A       93.184.216.34
www.example.com.  3600    IN    AAAA    2606:2800:21f:cb07:6820:80da:af6b:8b2c

Both versions of the domain resolve over both IPv4 and IPv6. Users get routed to whichever protocol their network supports.

How Dual-Stack DNS Resolution Works

When a client needs to resolve a domain, it typically sends two queries: one for the A record and one for the AAAA record. The client's operating system then decides which address to use based on a set of rules defined in RFC 6724 (address selection) and the "Happy Eyeballs" algorithm defined in RFC 8305.

Happy Eyeballs works like this: the client starts both an IPv6 and an IPv4 connection attempt simultaneously (or with IPv6 getting a small head start, usually 250ms). Whichever connection completes first wins. This prevents slow IPv6 connections from degrading the user experience, since the client can fall back to IPv4 quickly.

In practice, this means:

• If your server has both A and AAAA records and the user's network supports both protocols, the client will use whichever path is faster.
• If the user's network only supports IPv4, the AAAA record is ignored and the A record is used.
• If the user's network only supports IPv6, the A record is ignored and the AAAA record is used.

Publishing both record types is safe. There is no downside to having an AAAA record alongside your A record. Clients that cannot use IPv6 simply ignore it.

Common AAAA Record Mistakes

Adding an AAAA Record Without Actually Having IPv6

If you create an AAAA record pointing to an IPv6 address that your server does not actually listen on, IPv6 users will get connection timeouts. The DNS resolution succeeds, but the TCP connection fails. Happy Eyeballs will eventually fall back to IPv4, but that adds latency.

Only create AAAA records for addresses where your server is actively accepting connections.

Using IPv4-Mapped IPv6 Addresses

An IPv4-mapped IPv6 address looks like ::ffff:93.184.216.34. These are used internally by dual-stack software, not in DNS records. Your AAAA record should contain a real, routable IPv6 address.

Forgetting to Update AAAA Records During Migrations

When you migrate to a new server, you might remember to update the A record but forget the AAAA record. IPv6 users then get routed to the old server while IPv4 users reach the new one. This is especially tricky to debug because the problem is invisible if you are testing from an IPv4-only network.

Always update both A and AAAA records together during migrations. For a complete approach to managing DNS changes, see the DNS Record Types Reference.

Not Monitoring AAAA Records

If you are only monitoring your A records, you will miss problems that affect IPv6 users. AAAA records can be changed, deleted, or misconfigured just like any other record type. An attacker who modifies your AAAA record without touching the A record could redirect a large portion of your traffic without you noticing (if your monitoring only checks A records).

AAAA Records and CDNs

Most CDN providers handle AAAA records automatically. When you point your domain to a CDN using a CNAME or their specific DNS integration, the CDN's infrastructure provides both A and AAAA records at the edge. You do not need to manage IPv6 addresses manually.

For example, if you CNAME www.example.com to example.com.cdn.cloudflare.net, Cloudflare automatically serves both A and AAAA records for that hostname. The CDN handles IPv6 on your behalf, even if your origin server only supports IPv4.

This is one of the easiest ways to add IPv6 support: put a CDN in front of your site and let them handle the AAAA records.

AAAA Records and Email

AAAA records are not directly involved in email routing (that is handled by MX records and the A/AAAA records of the mail server hostnames). However, if your MX record points to mail.example.com, and mail.example.com has both A and AAAA records, email servers that support IPv6 will connect over IPv6.

This is generally fine. Most major email providers (Gmail, Outlook, Yahoo) support IPv6 for inbound and outbound mail. Just make sure the IPv6 address on your mail server has proper reverse DNS (PTR record) configured, as some mail servers reject connections from IPs without reverse DNS.

References

[1] S. Thomson, C. Huitema, V. Ksinant, M. Souissi. "DNS Extensions to Support IP Version 6." RFC 3596, October 2003. https://datatracker.ietf.org/doc/html/rfc3596

[2] R. Droms, Ed. "DNS Extensions to Support IPv6 Address Aggregation and Renumbering." RFC 2874. https://datatracker.ietf.org/doc/html/rfc2874

[3] D. Schinazi, T. Pauly. "Happy Eyeballs Version 2: Better Connectivity Using Concurrency." RFC 8305, December 2017. https://datatracker.ietf.org/doc/html/rfc8305

AAAA records are the IPv6 counterpart to A records. As IPv6 adoption crosses the 45% mark, they have gone from optional to increasingly important for performance and reliability.