NXDOMAIN
NXDOMAIN is the DNS response code (RFC 1035) a server returns when a queried domain name does not exist at all, as distinct from NOERROR with an empty answer, which means the name exists but has no record of the requested type. A resolver that receives NXDOMAIN for a name can cache that negative result for a TTL set by the queried zone's SOA record (RFC 2308), so repeated queries for a nonexistent name don't keep hitting authoritative servers. This caching is why a newly registered domain, or a typo'd one a registrar hasn't delegated yet, can keep returning NXDOMAIN for a while even after the correct delegation is published, and why some ISPs and public Wi-Fi networks intercept NXDOMAIN responses to redirect users to a search or ad page instead of returning the honest "this name doesn't exist" answer.
By AdminKit team, Netbase JSC · Updated