A CNAME record aliases one hostname to another. Instead of an IP, it returns a canonical name that the resolver then looks up in turn.
CNAME records are how you point a subdomain such as www or shop at a provider's hostname, for example your-store.myshopify.com or a CDN endpoint. The resolver follows the alias to the target name and resolves that target's A or AAAA records. This indirection means you can change where a subdomain lands by updating a single record on the provider's side, without touching your own IP addresses.
A key rule is that a CNAME cannot coexist with other records on the same name, which is why you cannot place a CNAME at the zone apex (the naked domain) alongside the required NS and SOA records. Providers work around this with flattening or ALIAS records. This checker shows the canonical target each resolver returns for your hostname, so you can confirm the alias is uniform worldwide and that no location is still pointing at a previous target. Mismatched CNAME targets across regions are a clear sign propagation is still in progress.
Frequently asked questions
- Why can't I use a CNAME on my root domain?
- The apex must hold NS and SOA records, and a CNAME cannot share a name with other records. Use ALIAS/flattening instead.
- Does a CNAME slow down resolution?
- It adds one lookup step, but the effect is negligible and usually cached.