The nameserver that holds the actual DNS records for your domain and answers queries about them. When someone looks up your domain, their recursive resolver asks an authoritative nameserver, "What's the IP for example.com?" and gets a definitive answer.
You point your domain at authoritative nameservers during registration. They host your zone file—the master copy of all your DNS records (A, MX, CNAME, etc.). There's no middleman; the authoritative server is the source of truth.
Most registrars run their own authoritative nameservers, but you can point to third-party ones (Cloudflare, Route53, your own hardware). At bunkerdomains, you can use our nameservers or your own. We don't force lock-in.
Why it matters: If your authoritative nameserver goes down or gets hijacked, your domain stops working. If you use a registrar's nameservers and they get politically pressured, your DNS can vanish. This is why some operators run private authoritative nameservers or use multiple providers in different jurisdictions. DNSSEC adds cryptographic proof that records haven't been tampered with.