Your IP address could not be determined at this time.

Registration Data Access Protocol (RDAP)


Registry Data Access Protocol (RDAP) is a Whois alternative for querying resource registration data from Domain Name Registries (DNRs) and Regional Internet Registries (RIRs) like ARIN. When you use RDAP to query registration data, responses are delivered in JavaScript Object Notation (JSON) format (instead of the text format provided by Whois). You also need a bootstrapping service, which determines the right place to send the RDAP query. ARIN provides both an RDAP client (NicInfo) and a bootstrap service (accessed when you query RDAP using the correct URL in your RDAP client).

Note: Note: RDAP does not have a web interface. To access RDAP, you need to install an RDAP client and use it to perform your queries.

How does RDAP differ from Whois?

  • RDAP is an HTTP-based REST-style protocol with standardized responses specified in JSON, whereas Whois is a text based protocol, utilizing a specialized protocol and port.
  • RDAP response data objects are easily translated into languages other than English, whereas Whois response data objects may not be.
  • RDAP responses offer direct referrals to other RIRs, whereas Whois defines no queries or responses, and interaction with DNRs and RIRs can vary significantly.

Is RDAP a RESTful Protocol?

RDAP meets the industry-accepted definition for a web-based RESTful protocol. It serves JSON responses over HTTP/HTTPS using URLs to distinguish various resources. The only HTTP methods used by RDAP are HEAD and GET.

Are there any RDAP clients available for me to use?

Yes. ARIN has written a command-line RDAP client called NicInfo.

In addition, there are clients available from DNSBelgium, CNNIC, and CentralNIC.

Query URLs

The correct URL preceding any query to ARIN's RDAP service is

Alternatively, you may use to query without using ARIN's bootstrap server.

RDAP Query: NicInfo Example

RDAP is a command-line tool. To query specifically against ARIN’s RDAP service, use:

nicinfo <object> --base

where <object> is an IP address, domain name, autonomous system number (ASN), nameserver host name, or entity identifier.

The returned response might look like the following example:

How do I search for...

A Domain?

Queries for domain information are of the form /domain/XXXX/...,where XXXX is a fully qualified (relative to the root) domain name.

An IP Address or Network?

Queries for information about IP networks are of the form /ip/XXX/...or /ip/XXX/YY/... where the path segment following 'ip' is either an IPv4 dotted decimal or IPv6 [RFC5952] address (i.e., XXX) or an IPv4 or IPv6 Classless Inter-domain Routing (CIDR) [RFC4632] notation address block (i.e., XXX/YY).

An Autonomous System Number (ASN)?

Queries for information regarding ASN registrations are of the form /autnum/XXX/... where XXX is an ASN

A Nameserver?

Queries for information about nameservers are of the form /nameserver/<nameserver name> where the <nameserver name> parameter represents a fully qualified host name as specified in RFC 0952 and RFC 1123. Internationalized names represented in either A-label or U-label format are also valid nameserver names.

A Point of Contact record (POC) or an Organization Identifier (Org ID)?

Queries for information about entities (POCs and Org IDs) are of the form /entity/<handle>, where the <handle> parameter represents the POC org Org ID handle (e.g., EXAMPLE123-ARIN).

For full details and specifications, please view the following IETF Internet Request for Comments (RFC) documents:

  • RFC 7480 - HTTP Usage in the Registration Data Access Protocol (RDAP)
  • RFC 7481 - Security Services for the Registration Data Access Protocol (RDAP)
  • RFC 7482 - Registration Data Access Protocol (RDAP) Query Format
  • RFC 7483 - JSON Responses for the Registration Data Access Protocol (RDAP)
  • RFC 7484 - Finding the Authoritative Registration Data (RDAP) Service
  • RFC 7485 - Inventory and Analysis of WHOIS Registration Objects

What is a bootstrap server?

A bootstrap server is a special type of server for helping clients find an authoritative server to query (this is called bootstrapping). Query bootstrapping can be an expensive process for some clients, and a bootstrap server can alleviate that expense by pre-loading the bootstrapping information. To utilize an RDAP bootstrap server, an RDAP client simply sends RDAP queries and receives HTTP redirects to the authoritative server.

Can I operate my own bootstrap server instead of using ARIN's directly?

Yes. The ARIN bootstrap server is open source and can be found on GitHub.

What are bootstrap files?

Bootstrap files are JSON files specified in RFC 7484. IANA publishes the following files:

  • Autonomous System Numbers
  • IPv4 Allocations
  • IPv6 Allocations
  • Domain Registries

What do I do if I have questions this page and the RFCs don't answer?

If you need help using the RDAP service, ARIN recommends subscribing and posting to the arin-tech-discuss mailing list. You may wish to check the mailing list archives before submitting your question.

Search Related Content

full site search.