Query authoritative registrar WHOIS records for any domain over port 43.
WHOIS Lookup talks directly to the correct registry WHOIS server for the domain’s TLD and returns the raw registration record — registrar, important dates, name servers and (where published) registrant contacts.
It picks the right server automatically from a built-in map of TLDs, falling back to IANA for anything unusual, so you get an accurate answer without guessing which WHOIS host to ask.
Most registrars now apply privacy/redaction in line with GDPR and similar laws, so personal contact fields are often masked. Dates, registrar and name servers remain visible.
Common TLDs route to their dedicated registry; anything else falls back to the IANA WHOIS server, which points you to the responsible registry.