Glossary / whois

WHOIS

The legacy port-43 protocol for querying domain registration records, now superseded by RDAP.

WHOIS dates to the early ARPANET era and returns unstructured plain text, which every consumer must parse with fragile, registry-specific rules. It has no standard schema, no authentication, and inconsistent rate limits.

For gTLDs, ICANN formally retired the port-43 WHOIS requirement in January 2025 in favor of RDAP. Many country-code TLDs still operate WHOIS services, which is why robust availability engines keep a fallback path.

When you see a domain tool advertise 'real-time WHOIS checks,' it is usually screen-scraping text. DomainFind.ai queries RDAP first and falls back to DNS-over-HTTPS signals, labeling every result with the method used.

Related terms

• RDAP (Registration Data Access Protocol) — The modern, HTTPS-based successor to WHOIS that returns structured JSON registration data.
• Domain Availability — Whether a domain can be registered right now at standard pricing.

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