What Is WHOIS?

WHOIS is a longstanding way to request information about a registered domain. A response may show dates, registrar, nameservers, status codes, and contact fields. It is a registration lookup, not a test that a website works or a guarantee that every field is public and current.

What a lookup can show

A response commonly includes the domain name, registrar and key registration events, such as creation or expiration. Status codes can indicate restrictions on transfer or updates. Nameserver fields describe delegation; they do not list every DNS record. For current A, MX, or TXT answers, use a DNS lookup instead.

Data depends on the registry, registrar, domain ending, and access rules. Some WHOIS responses are free-form text, so labels and formatting vary. A blank field is better treated as unknown than as proof that the underlying fact does not exist.

WHOIS and RDAP today

For generic top-level domains, RDAP is the current standardized registration-data service. It uses structured HTTP and JSON responses. Some domain endings may still require a WHOIS fallback. The RDAP comparison explains why the same domain can appear differently across the two methods.

Privacy rules may redact personal contact details or substitute a privacy-service contact. Redaction does not mean a domain has no registrant. Do not use a displayed contact address as an invitation to send unsolicited messages.

How to read a result responsibly

Enter the exact domain at /whois, note the source and lookup time if shown, and compare status and dates with the registrar when a business decision depends on them. An expiration date marks a registration event, not a guaranteed release for purchase. Likewise, a temporary lookup failure is not evidence that a domain is unregistered.

Keep raw responses private if they include personal data. For a practical walkthrough, see understanding lookup results.

Sources

• ICANN: RDAP information
• RFC 9083: RDAP JSON responses