Instantly check CNAME records to see alias mappings for domains. Our CNAME checker helps verify DNS entries and resolve domain pointing issues
A CNAME lookup shows which hostname a domain or subdomain is an alias of. A CNAME (canonical name) record says "this name is the same as that name": for example www.example.com → example.com, or shop.example.com → a hosted store's hostname. Resolvers follow the alias and use the target's own A or AAAA records.
www.example.com or blog.example.com.From a terminal: dig www.example.com CNAME.
example.com needs SOA and NS records, so it can't be a CNAME. DNS providers work around this with ALIAS/ANAME records or "CNAME flattening".Use a CNAME when you point a subdomain at a hostname run by someone else, such as a CDN or hosted service, so their IP changes don't require you to update anything. Use an A record when you control the server's IP.
Not under the DNS standards, because the root of a zone must hold SOA and NS records and a CNAME can't coexist with other records. Use your DNS provider's ALIAS, ANAME or CNAME-flattening feature instead.
Slightly, the first time: the resolver needs an extra lookup to resolve the target. After that both answers are cached, so the effect is negligible in practice.
The service the CNAME points to must have a certificate for your subdomain, not just its own hostname. Check what certificate is served with the SSL checker, and add the custom domain in the service's settings.