DNS Records & Concepts
What is an AAAA record?
An AAAA record, pronounced “quad-A record”, is a DNS record that maps a domain name or subdomain to an IPv6 address. It is the IPv6 equivalent of the A record, where an A record maps a domain to a four-number IPv4 address like 93.184.216.34, an AAAA record maps it to the longer hexadecimal IPv6 format like 2606:2800:220:1:248:1893:25c8:1946.
The four As in AAAA reflect the relationship to the A record, an IPv6 address is 128 bits long, four times the 32 bits of an IPv4 address. The AAAA record was named to reflect this: four times the address length, four As in the record type name.
AAAA records exist because the internet is in the process of transitioning from IPv4 to IPv6. IPv4 addresses, the four-number format that has been the foundation of internet addressing since the 1980s, are exhausted. The pool of available IPv4 addresses ran out years ago. IPv6 was developed to solve this problem, providing an effectively unlimited address space. As more devices, networks, and servers adopt IPv6, AAAA records become increasingly important alongside A records for ensuring domains are reachable across all parts of the modern internet.
How an AAAA record works
The mechanics of an AAAA record are identical to an A record, the only difference is the address format. When a browser resolves a domain it requests both A and AAAA records. If an AAAA record is present and the visitor’s network supports IPv6 the browser connects using the IPv6 address. If only an A record is present the browser uses the IPv4 address. If both are present the browser typically prefers IPv6, following a standard called Happy Eyeballs that tries both in parallel and uses whichever connects first.
When a visitor on an IPv6-capable network visits example.com the DNS resolution retrieves the AAAA record: 2606:2800:220:1:248:1893:25c8:1946, and the browser connects directly to that IPv6 address. The server at that address receives the request and responds. From the visitor’s perspective the experience is identical to an IPv4 connection, the address family used is invisible.
A DNS resolver looking up an AAAA record follows the same hierarchy as for an A record. It queries the authoritative nameserver for the domain and retrieves the AAAA record value. The result is cached for the record’s TTL duration before being refreshed.
IPv6 address format
Understanding the IPv6 address format helps explain why AAAA records look so different from A records and why IPv6 was necessary to replace IPv4.
IPv4 addresses: 32 bits, written as four groups of decimal numbers from 0 to 255 separated by dots. 93.184.216.34. There are approximately 4.3 billion possible IPv4 addresses, a number that seemed enormous in the 1980s but proved insufficient for the modern internet.
IPv6 addresses: 128 bits, written as eight groups of four hexadecimal digits separated by colons. 2606:2800:0220:0001:0248:1893:25c8:1946. IPv6 provides approximately 340 undecillion addresses, 340 followed by 36 zeros, enough for every device on earth to have many addresses with an essentially infinite supply remaining.
IPv6 addresses can be abbreviated according to specific rules. Leading zeros within each group can be omitted, 0220 becomes 220. Consecutive groups of all zeros can be collapsed to ::, but only once in an address. 2001:0000:0000:0000:0000:0000:0000:0001 becomes 2001::1.
The hexadecimal format of IPv6 addresses and their length make them impractical to type or remember directly, which is exactly why DNS exists. No one needs to know that google.com resolves to 2a00:1450:4009:821::200e for IPv6. The domain name is the human-readable handle and DNS handles the translation invisibly.
AAAA records and dual-stack connectivity
Most modern servers and hosting infrastructure support dual-stack connectivity: being reachable over both IPv4 and IPv6 simultaneously. A dual-stack domain has both an A record for IPv4 connectivity and an AAAA record for IPv6 connectivity. Any visitor can reach the server regardless of whether their network uses IPv4, IPv6, or both.
Configuring dual-stack DNS, both A and AAAA records, for a domain is straightforward. The same domain name gets two records of different types pointing to the server’s IPv4 and IPv6 addresses respectively.
Browsers and other clients that support dual-stack use the Happy Eyeballs algorithm: attempting both IPv4 and IPv6 connections simultaneously and using whichever responds first. If IPv6 is available and working it is typically preferred. If the IPv6 connection fails the browser falls back to IPv4 seamlessly. This fallback behaviour means having both records provides better reliability than either alone.
AAAA records and redirect management
AAAA records play the same role in redirect management as A records, they are one of the methods for connecting a domain to redirect infrastructure, specifically for IPv6 connectivity.
IPv6 coverage for redirect domains: if a redirect management service provides IPv6 addresses for its infrastructure alongside IPv4 addresses, configuring AAAA records in addition to A records ensures that visitors on IPv6 networks can reach the redirect service and receive the correct redirect responses.
CNAME as the preferred alternative: where possible CNAME records are preferred over both A and AAAA records for connecting domains to redirect management services. A CNAME pointing to the service’s hostname automatically resolves to whatever IP addresses the service currently uses, both IPv4 and IPv6, without requiring separate A and AAAA records. If the service updates its infrastructure IP addresses the CNAME continues to work without any DNS changes. This is why CNAME is the recommended connection method for subdomains and why the ALIAS/ANAME record pattern exists to provide similar functionality for apex domains.
Modern CDN support: platforms like Cloudflare assign both IPv4 and IPv6 addresses to all domains on their network automatically. Domains using Cloudflare for DNS and redirect management get AAAA record functionality without needing to manually configure AAAA records; Cloudflare handles IPv6 addressing as part of its infrastructure.
IPv6 adoption and why AAAA records matter
IPv6 adoption has been growing steadily and AAAA records are increasingly relevant for ensuring complete reachability across the modern internet.
Mobile networks: many mobile carriers, particularly in regions where IPv4 addresses are scarce, have deployed IPv6-only or IPv6-preferred networks. Visitors on these networks connect to websites over IPv6. A domain without an AAAA record is unreachable from pure IPv6 networks unless carrier-grade NAT or IPv4 translation is in place.
ISP deployment: major ISPs in the United States, Europe, and Asia have deployed IPv6 for residential customers. A significant and growing proportion of web traffic, estimates range from 30 to 45 percent depending on region and measurement methodology, uses IPv6.
Data centres and cloud providers: modern cloud providers and hosting platforms support IPv6 natively. Servers provisioned on AWS, Google Cloud, Azure, and other major providers can receive both IPv4 and IPv6 addresses. Configuring AAAA records for domains on these providers is straightforward.
SEO and performance: there is no direct SEO benefit to configuring AAAA records; search engines crawl and rank based on content and technical quality, not on IP address family. However ensuring complete reachability across all network types is part of good technical infrastructure. A site unreachable from significant portions of the internet is failing those visitors entirely.
Checking AAAA records
AAAA records are checked using the same tools as A records, specifying AAAA as the record type.
dig command: on Linux and macOS:
Returns the AAAA record for example.com including the IPv6 address value and TTL. Adding +short returns only the IPv6 address:
nslookup: on Windows and other platforms:
Online tools: web-based DNS lookup tools support AAAA record queries and show results from multiple geographic locations, useful for verifying that AAAA record changes have propagated globally.
Testing IPv6 connectivity: verifying that the IPv6 address in an AAAA record is actually reachable from an IPv6 network requires an IPv6-capable connection. Tools like curl with IPv6 support can test connectivity directly to an IPv6 address. curl -6 https://example.com forces curl to use IPv6, if it connects and retrieves content successfully the AAAA record and IPv6 connectivity are working correctly.
Common AAAA record issues
Missing AAAA record on IPv6-only networks: a domain without an AAAA record is unreachable from pure IPv6 networks. If the server supports IPv6 adding an AAAA record alongside the existing A record ensures complete reachability.
AAAA record pointing to wrong address: a misconfigured AAAA record pointing to an incorrect IPv6 address routes IPv6 visitors to the wrong server or a non-existent address. IPv6 connectivity fails while IPv4 continues to work. The asymmetric failure, working for some visitors but not others, can be difficult to diagnose without specifically testing from an IPv6 network.
IPv6 address not listening on the server: an AAAA record correctly pointing to the server’s IPv6 address but the server not configured to accept IPv6 connections results in connection failures for IPv6 visitors. Both the DNS record and the server configuration must be correct for IPv6 to work end to end.
SSL certificate not covering IPv6 endpoint: SSL certificates are issued for domain names rather than IP addresses, the same certificate covers both IPv4 and IPv6 connections as long as the server presents it correctly on both. However if the IPv4 and IPv6 addresses point to different servers, perhaps during a migration, the certificate must be present and correctly configured on both.
TTL mismatch between A and AAAA records: when both A and AAAA records exist for the same domain it is good practice to set matching TTLs on both. Mismatched TTLs mean one record is cached longer than the other, which can cause inconsistent behaviour during DNS updates when one record has propagated and the other has not.