WhoIs is both a protocol and a network of services & databases that answers the question, “Who is responsible for a particular domain name or ip address?” WhoIs has been and continues to be used for any or all of the following:

1. Display of information collected at the time a domain name or ip numbering resource¹ was registered.
2. The WhoIs protocol itself, as defined in RFC 3912 (previously RFC 954).
3. Public directory services that provide access to domain and ip address registration information.

The Way Forward: RDAP

RDAP is a modern, direct replacement for the mature WHOIS protocol. It overcomes the shortcomings associated with WHOIS in addition to adding new functionality not previously available.

Key Features of RDAP

• Data is returned in a standarized format, which is both machine and human readable. The machine readability aspect lends itself to processing by automated systems, security tools, and domain management software.
• Differentiated access is now available, allowing for different levels of information access for individual users and organizations.
• The protocol supports internationalized domain names and characters, providing native language support for non-Latin characters such as found in Devanagari (Hindi) and Cyrillic, which was a significant shortcoming of WHOIS.
• Query responses and any resulting errer messages are presented in a standardized format, thus eliminating differences sometimes found using different WhoIs services.

Until RDAP is fully adopted globally (notably by ccTLDs), it will likely be necessary to use both WhoIs and RDAP. For more details about TLDs, reference the Understanding Domains tutorial.
Further reading: RFC 7842 and RFC 7843