Thick WHOIS

In a thick WHOIS registry, the registry keeps the complete record: registrant name, address, email, nameservers, dates, everything. Query the registry and you get it all in one place. Most new gTLDs and many country codes work this way.

A thin registry stores only the basics, which registrar sponsors the name and the key dates, and points you to the registrar for the rest. .com and .net have always been thin, which is why a .com lookup has traditionally been a two-step process.

ICANN ordered .com and .net to go thick years ago. Then GDPR arrived, most contact data got redacted anyway, and the transition was shelved indefinitely. In practice the distinction matters less now than it did, since what you get back from either type is mostly "REDACTED FOR PRIVACY."