One hostname, two address formats
DNS helps a device find an IP address for a hostname such as www.example.com. Two common record types provide addresses: an A record contains an IPv4 address, while an AAAA record contains an IPv6 address. The names refer to the record types, not to different kinds of websites. Either record can point a hostname toward a server that provides the same site.
IPv4 addresses are 32 bits long and are usually written as four decimal numbers separated by dots, such as 192.0.2.34. IPv6 addresses are 128 bits long and are written as groups of hexadecimal digits separated by colons, such as 2001:db8::34. These particular addresses are for documentation examples; they are not addresses to use when configuring your site.
What an A or AAAA record actually does
An A record associates a DNS name with an IPv4 address. An AAAA record makes the corresponding association with an IPv6 address. For example, the name www.example.com could have an A record containing 192.0.2.34 and an AAAA record containing 2001:db8::34. A DNS query for A records asks for the first kind of address; a query for AAAA records asks for the second.
Neither record says which web page to display, which port to use, or whether a server will accept a connection. DNS supplies address information; the browser and network then have more work to do. Also, each hostname needs its own relevant DNS setup. A record for example.com does not, by itself, create a record for www.example.com. A hostname may have multiple A records, multiple AAAA records, both types, or neither, depending on how the service is arranged.
Why a site might publish both
A hostname with both A and AAAA records is often described as dual-stack. It gives clients address information for IPv4 and IPv6. A client may request both types and choose a connection path based on its network capabilities and connection behavior. Publishing both records does not force every visitor to use IPv6, and the order in which records appear in a lookup is not a reliable way to control that choice.
A site does not need an AAAA record merely because IPv6 exists. Add one when the destination server or service is configured to receive traffic at the stated IPv6 address and the route to it works. An incorrect AAAA record can cause trouble for visitors whose devices attempt IPv6, even while the IPv4 address works. Likewise, an A record should point to an IPv4 destination that is ready to serve the intended hostname.
Reading records in a DNS control panel
A DNS control panel commonly asks for a record type, a name or host field, a value, and a time to live (TTL). For an A record, the value is an IPv4 address; for an AAAA record, it is an IPv6 address. The name field identifies the hostname being configured. Panels vary in how they represent the domain itself and subdomains, so check the complete hostname the panel displays before saving.
TTL tells caching DNS resolvers how long they may keep a record before asking again. A record change therefore may not appear to every user at once. If you are replacing an address, remember to review both record types: updating the A record does not update the AAAA record. A stale AAAA record can continue pointing some connections toward an old destination.
A practical way to troubleshoot
Start by checking the exact hostname that fails, rather than assuming the domain and its www name are identical. Query its A and AAAA records separately using a DNS lookup tool. For example, dig www.example.com A and dig www.example.com AAAA show the two answer types independently. Compare the returned values with the addresses assigned to your service. If an answer is missing or unexpected, check the corresponding record in the authoritative DNS configuration.
If the DNS answers look right but the site still fails, test connectivity over IPv4 and IPv6 separately where your tools and network allow it. A DNS record can be correct while a firewall, server configuration, or network route prevents a connection. Conversely, an absent AAAA record is not necessarily an error if the service is intended to use IPv4 only. Treat DNS results as one part of the diagnosis, not proof that either connection path works end to end.
