- WHOIS
- A query and response protocol (RFC 3912) used to look up registered users or assignees of an internet resource such as a domain name or IP address block. WHOIS servers respond on TCP port 43 with text records.
- RDAP
- Registration Data Access Protocol (RFC 7480-7484) — the modern successor to WHOIS that returns structured JSON data over HTTPS, supports authentication, internationalization, and is the required protocol for new gTLDs.
- Registrar
- An ICANN-accredited organization that sells domain registrations to end users (e.g. GoDaddy, Namecheap, Cloudflare Registrar) and submits registration data to the registry.
- Registry
- The organization that operates the master database for a specific TLD (e.g. Verisign for .com, PIR for .org). Registrars push records into the registry via EPP.
- EPP status codes
- Extensible Provisioning Protocol status flags such as clientTransferProhibited, serverHold, and redemptionPeriod that describe the current state of a domain registration.
- Redemption period
- A 30-day grace window after a domain expires during which the original owner can recover it by paying a redemption fee, typically $80-$200 above normal renewal cost.
- Name server (NS)
- DNS servers authoritative for a domain. WHOIS lists which name servers the domain is delegated to at the registry level.
- GDPR redaction
- Privacy masking applied to WHOIS records for EU-based registrants under the General Data Protection Regulation, replacing personal contact details with proxy values.