CNAME

In short: A DNS record type that points a name as an alias to another domain name, instead of directly to an IP address.

In more detail: For example, wiki.emzett-digital.com can point via CNAME to emzett-digital.com — the actual IP resolution then happens via the target record. According to the standard, a CNAME must not exist alongside other record types (e.g. MX) for the same name — a common source of error in DNS configuration.

In Depth

wiki.emzett-digital.com.   3600   IN   CNAME   emzett-digital.com.

When resolving, a CNAME is always “followed” through to the end (a chain), until a record without a further CNAME remains — usually an A record or AAAA record. Long CNAME chains (CNAME points to CNAME points to CNAME …) are allowed, but slow down every resolution by an additional lookup per link, and are a common, hard-to-find cause of slow load times.

The most important practical pitfall: according to RFC 1034, a CNAME must not exist alongside another record type for the same name — so you can’t set both a CNAME and, say, an MX record for wiki.emzett-digital.com at the same time. This regularly causes configuration errors when setting up email on a subdomain managed via CNAME. For the root domain itself (emzett-digital.com without a subdomain), a CNAME is even technically completely forbidden — only provider-specific alternatives like “ALIAS” or “ANAME” records help there.

See also: DNS Records, Subdomain, A Record