CNAME lookup

What a CNAME record is

A CNAME points one hostname at another hostname, rather than directly at an address. Resolving it means following the alias to whatever it names, then resolving THAT name's own records - which is why a CNAME chain can be several hops before it reaches an A or AAAA record.

Why it is used

It lets a service change its underlying servers (and their IP addresses) without every customer having to update their own DNS - a CDN, a hosting platform or an email provider typically has customers CNAME a subdomain to them, and the provider is then free to move that infrastructure at will.

A rule worth knowing

A name that has a CNAME record cannot also have other records at that exact name (the "CNAME cannot coexist" rule) - which is the usual reason a root domain (example.com, without a subdomain) uses an A record rather than a CNAME even when pointing at a service that would prefer one.

Related tools

See A lookup for where a chain of aliases eventually lands, or DNS lookup for the whole picture.