DNS A and AAAA records

What it means

An A record associates a DNS name with an IPv4 address. An AAAA record associates a DNS name with an IPv6 address. They are separate DNS record types: one hostname can publish A records, AAAA records, both or neither. DNS provides candidate addresses; reachability, network selection and the web server's listening configuration determine whether a connection succeeds. A record AAAA record

Try it

Example — inspect both address families. These addresses are reserved documentation examples and are not real endpoints. The sample represents DNS data, not an active query.

www.example.com.  300 IN A     192.0.2.25
www.example.com.  300 IN AAAA  2001:db8::25

The TTL displayed here is 300 seconds for each record in this simple illustration. A browser on one network may successfully connect using an IPv4 address; another network may attempt IPv6. Address-family selection and fallback depend on client and network behavior, not on an unconditional DNS rule that AAAA is preferred. IPv4 example allocation IPv6 example allocation

Compare the two record types

A record set may contain multiple addresses. Having a syntactically valid AAAA record does not mean the IPv6 endpoint is reachable from the public Internet or configured to serve the hostname. Equally, deleting AAAA simply to hide a routing problem may harm clients that use IPv6; investigate first.

In practice

When some visitors can open a site and others cannot, compare A and AAAA answers separately and ask whether the origin or CDN listens on both advertised address families. A DNS response alone cannot show the HTTP status, TLS certificate or network route. Obtain actual approved destination addresses from the hosting provider and validate HTTPS for the intended hostname before changing records.

For connection setup consult Connect a domain to a website. If the site only fails for certain visitors, follow A website works for some visitors only, not an assumption that either address family must always win.