A CNAME record makes one name an alias of another name. Anyone asking for the alias is sent on to the target.
If www.example.com is a CNAME for another name, a lookup for www.example.com follows that name and returns whatever records it has. The alias has no address of its own.
A name that has a CNAME cannot hold other records at the same name. That is why the bare domain, which needs records such as MX and NS, usually cannot be a CNAME.
Services often ask you to point a subdomain to them with a CNAME. Email providers sometimes publish DKIM keys that way: you add a CNAME at the selector name, and it points to a record on the provider's side.
Putting a CNAME at the bare domain, or next to an MX record on the same name, causes problems. A typing error in the target name makes the alias lead nowhere.
DNS Domain Detective lists the CNAMEs of a domain so you can see where each alias points. Open DNS Domain Detective
DNS Domain Detective is now available on the App Store.
Last reviewed: 2026-11-02
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