CNAME Lookup

Enter a subdomain name and see the whole CNAME chain down to the final address, not just the first step. Each step shows the record's time to live and the platform it points to. If you enter the domain itself, the tool also checks common names: www, mail, autodiscover and others.

Why a CNAME cannot exist on the domain itself

According to RFC 1034, a name with a CNAME carries no other records. A domain must have SOA and NS records, so there is no room left for an alias. Some resolvers will refuse to serve such a zone, and mail and signatures stop working. The alias goes on a subdomain.

Dangling alias

If the target does not exist, the name simply fails to open. It is worse when the target sits on a platform that hands out names on request: an outsider claims it and gets your subdomain along with the certificate and your visitors' trust. The check flags such targets separately.

What else you can see

Records next to the same name are queried at the domain's own name server. A regular resolver follows the CNAME itself and shows the target's records, so a violation cannot be spotted through it. A loop and a chain longer than ten steps are shown separately, because such resolvers cut them off.