CNAME What is a CNAME Record?
A CNAME record creates a hostname alias pointing to another hostname. Learn when to use CNAMEs, the zone apex limitation, and how ALIAS records work.
What is a CNAME record?
A CNAME (Canonical Name) record creates an alias from one hostname to another. Instead of pointing to an IP address directly, a CNAME points to a target hostname which is then resolved through its own DNS records.
CNAMEs are useful when you want multiple names to resolve to the same IP without duplicating A records everywhere — change the A record in one place and all CNAMEs update automatically.
Anatomy of a CNAME record
www.example.com. 3600 IN CNAME example.com.| Field | Value | Description |
|---|---|---|
| Name | www.example.com. | The alias — the name being looked up. |
| TTL | 3600 | Time-to-live in seconds. |
| Class | IN | Internet class. |
| Type | CNAME | Record type. |
| Target | example.com. | The canonical name to resolve. The resolver then looks up this hostname's A/AAAA records. |
Common uses
- www subdomain —
www.example.com→example.comso both resolve to the same server. - CDN aliases — Point
assets.example.comto your CDN's domain (e.g.example.cdn.com) so CDN IP changes don't require DNS updates on your side. - SaaS service aliases — Many services ask you to add a CNAME to map your custom domain to their infrastructure (e.g.
blog.example.com→customer.ghost.io).
The zone apex restriction
A CNAME record cannot be placed at the zone apex (the root domain itself, e.g. example.com without www). This is a hard DNS specification limit. The reason: a zone apex must have SOA and NS records, and a CNAME cannot coexist with any other record type at the same name.
Some DNS providers offer a proprietary workaround called ALIAS, ANAME, or CNAME flattening. These appear as normal A/AAAA records to the outside world but behave like CNAMEs internally, allowing root domain aliasing.
CNAME chains
A CNAME can point to another CNAME, creating a chain. Resolvers follow the chain until they reach an A or AAAA record. Chains add latency — one extra DNS lookup per hop. Keep chains to a minimum (ideally zero).
Common mistakes
- CNAME at the zone apex — Not allowed by RFC. Use ALIAS/ANAME or an A record instead.
- CNAME coexisting with other records — A CNAME at a given name cannot share that name with any other record type. If you add a CNAME for
mail.example.com, you can't also add an A record for it. - MX or NS pointing to a CNAME target — MX and NS records should not reference CNAME targets per RFC 2181. Use A records for mail and nameserver hostnames.
Frequently asked questions
Can a CNAME point to an IP address?
No. A CNAME must point to a hostname, not an IP address. Use an A record to point to an IP.
What is CNAME flattening?
CNAME flattening (also called ALIAS or ANAME depending on the DNS provider) is a proprietary feature that lets you use a CNAME-like alias at the root domain. The DNS provider resolves it server-side and returns A/AAAA records, staying within the DNS spec.
Does a CNAME affect TTL?
Both the CNAME record and its target A record have their own TTLs. The effective TTL for the resolved IP is the lower of the two.