CNAME Record Reference
This article is a reference for the formal structure, restrictions, and key technical details of a CNAME (Canonical Name) record.
CNAME record format
A CNAME record is a single resource record that maps one domain name to another. The structure follows the standard format defined in RFC 1035, Section 3.3.1.
The core component of a CNAME record is its RDATA (Resource Data) section, which is composed of one single element:
| Element | Description |
|---|---|
| domain-name | A domain name that specifies the canonical or primary name for the record. |
The canonical representation of a CNAME record is:
<name> IN CNAME <domain-name>
In the DNSimple record editor, a CNAME record is represented by the following customizable elements:
| Element | Description |
|---|---|
| Name | The host name for the record, without the domain name. This is generally referred to as a “subdomain”. |
| TTL | The time-to-live in seconds. This is the amount of time the record is allowed to be cached by a resolver. |
| Content | The fully-qualified domain-name that the CNAME maps to. |
CNAME record restrictions
Understanding the following restrictions is critical to properly using CNAME records:
-
No coexistence with other records: A CNAME record cannot coexist with any other record for the same name. It’s not possible to have both a CNAME and an MX record for
www.example.comsimultaneously. - Must point to a domain name: A CNAME record must always point to another domain name and never directly to an IP address.
-
Chained CNAMEs: A CNAME record can technically point to another CNAME record (e.g.,
a.example.comCNAMEb.example.com, andb.example.comCNAMEc.example.com). However, this is generally not recommended for performance reasons.
Have more questions?
If you have additional questions or need any assistance with your CNAME records, just contact support, and we’ll be happy to help.