NS Record

An NS record (Name Server) tells the DNS system which authoritative servers are responsible for a given domain. When a resolver needs to answer a query for example.com, it first asks the parent zone (the TLD, here .com) for the domain's NS records, then contacts one of those name servers to retrieve the actual A, MX or TXT records.

NS records exist in two places at once: at the parent zone as a *delegation*, and inside the child zone itself as part of the authoritative NS RRset. The parent's copy is what makes the delegation work; the child's copy is what is returned in normal answers. When the name servers live inside the delegated domain — for example ns1.example.com for example.com — the parent must also publish *glue records*, A/AAAA records for those name servers, to avoid a chicken-and-egg lookup.

Most domains list at least two name servers, and large operators distribute them across networks or use anycast so that a single outage cannot make the zone unreachable. NS changes propagate more slowly than ordinary DNS changes: resolvers cache the parent's delegation according to its TTL, and registrars typically push updates to the TLD once per day. A planned name-server migration therefore usually keeps both old and new servers serving identical data for several days while caches expire.

NS records work alongside the SOA record, which marks the zone apex and identifies the primary authoritative server, and ultimately decide which infrastructure controls every other record in the zone.