WHOIS dates back to 1982 and is fundamentally broken: plain text format that varies between registries, no authentication, no rate limiting, no privacy controls. RDAP is the IETF's replacement, standardized in 2015 (RFCs 7480-7484).
What RDAP improves over WHOIS:
- JSON output — structured, predictable, parseable. No more parsing 50 different free-text formats.
- HTTPS transport — encrypted, supports authentication, ratelimit-able.
- Differential access — the protocol explicitly supports returning different data to authenticated vs. anonymous queries. Law enforcement and IP rights holders can request full data; everyone else gets the redacted set.
- Pagination, search, redirects — modern HTTP semantics.
- i18n support — Unicode handling baked in.
ICANN required all gTLD registrars to support RDAP alongside WHOIS by 2019. WHOIS is still operational (legacy clients and tools rely on it) but new tooling should target RDAP.
RDAP queries are HTTPS GETs to https://rdap.registrar.com/domain/example.com — the response is structured JSON with the registrant data, nameservers, important dates, and status flags.
For end users, you almost never interact with RDAP directly. It's relevant if you're building tooling that queries domain data, or you want better privacy than WHOIS provides (ICANN's 2024 Registration Data Policy made RDAP the default response format for compliant registrars).
