Registration data explained
What is WHOIS—and why does RDAP matter now?
Reviewed 10 September 2026 · 7-minute read
WHOIS is a legacy text protocol for registration data; RDAP is its HTTPS/JSON replacement. A modern lookup can show whether a registration record exists and return public fields such as registrar, dates, status and name servers. It may not reveal a registrant, and a no-match response is not a purchase guarantee.
WHOIS and RDAP compared
| Characteristic | WHOIS | RDAP |
|---|---|---|
| Transport | TCP port 43 | HTTPS |
| Response | Registry-specific text | Structured JSON |
| Service discovery | Client-specific referral logic | IANA bootstrap registries |
| Error handling | Text markers vary | HTTP status plus RDAP response rules |
| Internationalization/access | Limited and inconsistent | Defined query, response and access-control model |
Why RDAP is now the primary path
ICANN describes RDAP as the replacement for WHOIS. All gTLD registries and registrars must provide RDAP, while most gTLD WHOIS service requirements ended on 28 January 2025. Some exceptions and voluntary WHOIS services remain, and country-code TLD operators are governed by their own policies.
SeekDom therefore resolves an RDAP endpoint from the IANA DNS bootstrap registry first. It only calls port-43 WHOIS when no RDAP service is known for that TLD.
What a public registration record can contain
- The queried domain and registry identifier
- Sponsoring registrar, if supplied
- Registration, update and registry-expiry events
- Domain status codes
- Authoritative name servers
- Notices, remarks and links to authoritative services
Fields vary by registry and access level. An expiry date is not a forecast that the domain will become purchasable on that date: renewal, grace, redemption, transfer, auction and registry rules can intervene.
Why the registrant may be hidden
ICANN's Registration Data Policy, effective since 21 August 2025 and revised in 2026, defines when contracted gTLD parties must or may redact personal data in public registration output. Country-code policies and applicable law can differ. Public lookup data is therefore useful operational evidence, not a universal directory of domain owners.
What a lookup cannot prove
- Legal ownership, trademark rights or authorization to use a name
- That a no-record name is eligible, standard-priced or purchasable
- That a registered domain will drop on its displayed expiry date
- That missing public contact fields do not exist privately
- That a failed lookup means anything about registration status
Frequently asked questions
Is WHOIS still used?
Yes, but RDAP is now the primary standardized registration-data protocol. Since 28 January 2025, gTLD registries and registrars generally are no longer required to provide WHOIS, with limited exceptions; country-code operators follow their own rules.
Does a registration lookup show who owns a domain?
Not necessarily. Public results can show registrar, dates, status and name servers, while registrant fields may be redacted or absent. A public record is not proof of legal ownership.
Does an RDAP 404 guarantee a domain can be registered?
No. It means the RDAP service did not return a record for the exact query. Reserved names, premium rules, eligibility, syntax, pricing and a later registration can still prevent purchase.