WHOIS vs RDAP

They answer the same question — who registered this domain — but RDAP does it in a way built for the modern, privacy-regulated internet.

Format

WHOIS returns free-form text with no guaranteed structure; every registry laid it out differently, which made reliable parsing a constant headache. RDAP returns structured JSON with defined fields, so the same code works across every registry.

Transport

WHOIS runs over port 43, a protocol predating the modern web. RDAP runs over standard HTTPS, so it benefits from TLS encryption, caching, and the same tooling as any web API.

Internationalisation

WHOIS had no consistent handling of non-ASCII characters. RDAP supports internationalised domain names and Unicode properly, which matters for a global namespace.

Privacy and access

RDAP was designed with differentiated access in mind, fitting the post-GDPR world where registrant details are redacted by default. WHOIS had no native model for this — privacy was bolted on awkwardly.

The transition

ICANN mandated RDAP for gTLD registries, and it became the authoritative source for generic TLDs in early 2025. WHOIS still exists for some country-code TLDs that haven't migrated, which is why a complete lookup tool falls back to it when no RDAP server is available.

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