ALIAS, ANAME and Flattening
Why a CNAME Cannot Sit at the Root
A DNS alias record, often written as ALIAS or ANAME, lets a bare domain point to another hostname, something a standard CNAME cannot do. These record types are provider features that give the root domain some of the flexibility CNAME records give to subdomains.
The problem starts with the zone apex, the bare domain such as example.com. Every zone must hold SOA and NS records at its apex, and a CNAME cannot share a name with other records. A site hosted on a platform that only gives a hostname, such as sites.platform.example, therefore cannot be reached from example.com through a plain CNAME. The platform's addresses can also change, so a fixed A record may break when they do.
How ALIAS, ANAME and Flattening Work
These approaches differ in naming but share one idea: the DNS provider, not the visitor's resolver, follows the target name and publishes the result under the root domain.
- ALIAS and ANAME are names for provider-specific record types. When someone asks for the root domain, the provider's servers resolve the target and return the matching address records.
- CNAME flattening is a feature where the provider accepts a normal CNAME at the apex in its own control panel, then serves the target's resolved A and AAAA records as ordinary address records.
In all cases, a visitor's resolver receives plain A or AAAA answers, which is why the setup works with standard clients. The cost is that the provider must keep those addresses current, usually by re-checking the target on a schedule you cannot control in detail. Compare this with a standard CNAME record, which is simply followed by the resolver.
Trade-offs and Practical Options for the Root Domain
Provider-specific records are convenient, but they have trade-offs that matter when you choose a DNS host:
- Portability: The record is not part of the standard set, so moving to another DNS provider may mean rebuilding it as plain A records.
- Freshness: Address updates depend on the provider's refresh schedule, followed by the TTL that resolvers cache.
- Support: Not every provider offers these records, and the exact behavior differs between them.
For a root domain, the usual options are a fixed A record when the server address is stable, or an ALIAS-style record when the platform's address changes and your provider supports it. Read about choosing a managed DNS provider before you decide.
Frequently asked questions
Is an ALIAS Record a Standard DNS Record Type?
No. ALIAS and ANAME are not record types defined for every DNS server. They are provider features, and each provider implements them differently. Other servers never see the ALIAS itself, only the address records the provider returns. Check your provider's documentation for the exact behavior.
Does an ALIAS Record Update When the Target Changes?
Usually, but not instantly. The provider re-checks the target name on its own schedule, and resolvers keep the resulting address for as long as its TTL allows. A change may therefore take a while to reach every visitor, in the same way as any other DNS change.