CNAME record
The DNS record that makes one name an alias of another, so lookups for the alias continue at the target name.
What it means
A CNAME says a name is an alias: resolvers asked for any record at that name follow the CNAME and return the target's records. RFC 1034 forbids other data at a name that has a CNAME, which is why a CNAME cannot sit at the zone apex (where SOA and NS records must exist) and why a name with a CNAME cannot also carry a TXT record.
Mail providers use CNAMEs to manage records for you: Microsoft 365 and many sending platforms ask for selector._domainkey CNAMEs pointing at keys they host, so they can rotate keys without your involvement. Tracking and return-path subdomains can be CNAMEs too.
MX and NS records must point to real host names, never to a CNAME (RFC 2181).
Example
s1._domainkey.example.com. 3600 IN CNAME s1.domainkey.u123.mail.example.net.Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 1034: Domain Names: Concepts and Facilities, section 3.6.2rfc-editor.org
- RFC 2181: Clarifications to the DNS Specification, section 10.3rfc-editor.org
- RFC 9499: DNS Terminology, section 2rfc-editor.org
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