Traditional WHOIS returns human-formatted text whose labels and referral behavior vary between registries and registrars. RDAP returns JSON with standardized events, entities, status codes, notices and links.
Why results can differ
A registry may publish the domain lifecycle and registrar while the registrar publishes additional contact fields. Privacy law, proxy services and registry policy can redact either response. A tool should follow RDAP links when available and show missing values honestly.
Which source should you trust?
Use the registry for authoritative domain status and lifecycle data. Use the sponsoring registrar for registrar-managed contact information. Neither a WHOIS nor RDAP record proves that the listed party operates the website currently served by the domain.