DNS Checker

Which record answers which question

A / AAAA - where the domain actually points (IPv4/IPv6); the TTL next to each answer is how long resolvers may cache it, which is why DNS changes take time to land. CNAME - the alias chain, and the usual suspect when a subdomain "points at the wrong thing". MX - where this domain's mail goes, in priority order; the lookup to run before anyone reports missing email. TXT - SPF, DKIM, and domain-verification strings; most deliverability problems are diagnosed here. NS - which nameservers are authoritative, the record that decides whether anything else can be right. SOA - zone metadata; the serial number changing is how you confirm an edit was actually published. CAA - which certificate authorities may issue for the domain; a wrong CAA silently breaks certificate renewal, a failure mode worth monitoring for.

Reading a mismatch

Right after you change a record, disagreement between resolvers is expected: each cache serves the old answer until its TTL runs out, so propagation completes over minutes to hours depending on the previous TTL. Persistent disagreement is different - it usually means the change was made at only one of two nameserver providers, an old nameserver is still listed at the registrar, or a resolver is serving stale data past TTL. Round-robin and geo-routed setups also legitimately return different A records per query; check whether the set is stable rather than the order. And if the domain itself is the problem - lapsed registration takes the whole zone with it - that's the domain expiry checker's department.