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WHOIS and Registration Data Directory Services

The term "WHOIS" is not an acronym, but a service that asks and answers the question, who is responsible for that domain name or Internet Protocol (IP) address? WHOIS refers to the protocols, services, and data types associated with Internet naming and numbering resources including domain names, IP addresses, and Autonomous System Numbers (ASNs). Historically, the term WHOIS has been used to refer to any of the following:

  1. The information collected at the time of registration of a domain name or IP numbering resource, subsequently made available via a public directory service, and potentially updated throughout the life of the resource;
  2. The WHOIS protocol itself, which is defined in Request for Comments (RFC) 3912; or
  3. Public directory services that provide access to domain name registration information typically via applications that implement the WHOIS protocol or a web-based interface.

The ambiguities inherent in the WHOIS label complicate efforts to shape the evolution of meta-data for Internet naming and numbering. To address this, the ICANN organization (org) and the ICANN community developed more precise terminology for generic top-level domains (gTLDs).

For clarity, registration data refers to the information that is collected or generated in relation to a registered domain name. Registration Data Directory Services (RDDS) refer to the collective service(s) offered by registries and registrars to provide access to registration data (or a subset thereof), including the WHOIS service (where offered).

ICANN and Registration Data Services

To have a unique presence on the Internet, such as a website, email address, or online service, registrants (individuals or organizations that register a domain name) use a domain name registrar (companies that register domain names) or reseller (companies that offer domain name registration services through a registrar). This allows them to register a specific domain name that can be used for personal or commercial purposes. When registering a domain name, a registrar must collect or generate certain data associated with that gTLD domain name.

The Registration Data Directory Services (RDDS) system is a set of independently operated and distributed databases that are responsible for their portion of the Internet's identifiers, the responsible parties being known as registrars and registries. There are two categories of distributed databases:

  1. Domain names
  2. Internet Protocol numbers

The distributed databases associated with Internet numbers (IPv4 and IPv6 addresses, and ASNs), are not addressed here, other than to say that they are independently operated and unassociated with the domain name databases.

ICANN operates a free Registration Data Lookup Tool that allows end users to look up publicly available registration data, such as the name and contact information for the owner of a particular domain. The lookup tool provides the convenience of a simple and consistent interface at a single location for users to find information about a specific domain name registration, IP network, or an ASN.

Technical Overview of RDDS and WHOIS

ICANN requires accredited registrars and gTLD registries to comply with technical specifications for their RDDS, as described in ICANN's contracts. These specifications include service level agreements, formatting requirements, and access protocols.

You can find the technical specification of the WHOIS protocol described in detail in a document called "Request for Comments 3912" (RFC 3912), which was published in 2004. The WHOIS protocol lacks many of the protocol design attributes ( e.g., internationalization and strong security) that would be expected from any recently designed Internet Engineering Task Force (IETF) protocol. It should be noted that the WHOIS requirements will be phased out in 2025 for gTLD registries and registrars.

In 2010, the ICANN community held discussions about the need for the technical evolution of the WHOIS service. In March 2015, the Web Extensible Internet Registration Data Service (WEIRDS) working group published documents (RFCs) defining the Registration Data Access Protocol (RDAP), a standardized replacement for the WHOIS protocol. RDAP delivers registration data like WHOIS, but its implementation will change and standardize data access and query response formats.

On 30 April 2023, the ICANN Board adopted the proposed RDAP global amendments to registrar and registry agreements. The proposed amendments specified operational requirements for providing RDDS services via RDAP, and to phase out on 28 January 2025 certain obligations to provide RDDS via the WHOIS protocols. The amendments were the culmination of a long-standing commitment to the Internet community to improve the WHOIS system by replacing the WHOIS protocols with a better underlying technology – RDAP.

Learn more about RDAP here.

Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"""" is not an IDN."