DNS ALIAS Record

What is a ALIAS Record?

A DNS ALIAS record (also known as ANAME or virtual CNAME) is a proprietary DNS record type that provides CNAME-like functionality at the zone apex (root domain). Since standard CNAME records cannot coexist with other record types and the zone apex requires SOA and NS records, CNAME records cannot be used at the bare domain (e.g., example.com). ALIAS records solve this limitation.

When a DNS server receives a query for a domain with an ALIAS record, it resolves the target domain in the background and returns the resulting IP addresses as if they were A/AAAA records. This happens server-side, so the client never sees the ALIAS — it only sees standard A or AAAA records. This is fundamentally different from a CNAME, where the alias resolution is visible to and performed by the client's resolver.

ALIAS records are not defined in any RFC and are implemented differently by various DNS providers. Cloudflare calls their implementation "CNAME flattening," AWS Route 53 uses "alias records," and DNSimple and NS1 call them "ALIAS records." While the behavior is similar across providers, ALIAS records are not transferable between DNS providers because they are not part of the standard DNS protocol. The IETF has been working on standardizing this functionality through SVCB and HTTPS record types (RFC 9460).

Syntax & Examples

ALIAS record syntax varies by DNS provider since it's not standardized. Common representations:

; DNSimple / NS1 / Dyn style
example.com.    3600    IN    ALIAS    cdn.example.net.

; AWS Route 53 (configured via console/API, not standard zone format)
example.com.    A    ALIAS d111111abcdef8.cloudfront.net.

; Cloudflare (CNAME flattening - uses CNAME syntax at apex)
example.com.    3600    IN    CNAME    cdn.example.net.  ; automatically flattened to A/AAAA

The key difference from CNAME is that the DNS server resolves the target and returns A/AAAA records to the client, rather than returning a CNAME response. The client sees: example.com. 300 IN A 192.0.2.1 (the resolved IP of the target).

How to Query ALIAS Records

Since ALIAS records are resolved server-side, you cannot directly query for an ALIAS record type — clients always see the resulting A or AAAA records. To check if a domain is using ALIAS records, query for A records: dig example.com A. If the IPs match a CDN or other service's IP range, an ALIAS record may be in use.

To verify, compare the A records of the root domain with the suspected target: dig example.com A and dig cdn.example.net A. If they return the same IPs, an ALIAS record likely exists. You can also check with: dig example.com CNAME — if there's no CNAME response for the root domain but the IPs match another domain, it's likely an ALIAS. Some DNS providers expose ALIAS records through their API but not through standard DNS queries.

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