DNS CNAME checker
With this online tool, you can find the CNAME record for any domain name or subdomain. When you enter the domain in the input field below, it will show whether or not a canonical name is configured for that domain.
What are CNAME records and how do they work?
The DNS CNAME record can be configured to delegate the configuration of DNS records to some other DNS zone. In other words, it tells DNS clients (like web browsers) to query the DNS records of a different domain, and treat them as if they were for the domain with the CNAME record.
The most common use case for this is when you want to configure a custom domain name for a third party service. In this case you control your domain name, but the third party service controls the servers that host it. It would be inconvenient if you'd have to change your DNS settings whenever this service changes its IP addresses. This is why they commonly request you to create a CNAME record instead. That way you remain in control of your domain name, but they can change the DNS configuration of their service at any time. When such a record exists for a domain name or subdomain, the content of the record is said to be the canonical name of that domain.
Restrictions on CNAME records
There are a couple of restrictions on the configuration of CNAME records:
- At most one CNAME record may exist for any domain or subdomain. See section 10.1 of RFC 2181.
- The content of a CNAME record must be a valid domain name. It cannot be an ip address. See section 3.6 of RFC 1034.
- If a CNAME record is present, no other records may be present, except for DNSSEC records (RRSIG, DNSKEY, DS, NSEC and NSEC3PARAM). See section 10.1 of RFC 2181.
- Root domains should not have a CNAME record. Because of the previous restriction, the root domain could no longer have NS or SOA records.
- MX and NS records must not point to a domain name that has a CNAME record. See section 10.3 of RFC 2181.