Frequently Asked Questions about Whois-RWS

As of 2019, ARIN strongly recommends using Whois/RDAP because of its standardization, support for security, and access to registration information from other RIRs, registrars, and organizations who support RDAP.

What is Whois-RWS?

ARIN provides a Representational State Transfer (REST)ful interface for Whois queries (Whois-RWS). RESTful systems usually utilize URLs that are sent using an Application Programming Interface (API). ARIN’s Whois-RWS can be accessed through its web interface with a browser or through command line scripts.

Will the NICNAME/WHOIS TCP port 43 service be turned off in the near future?

No. ARIN realizes that many long-term customers use this service. ARIN has no plans to retire it in the near future. For those who rely on existing scripts and clients, ARIN will continue to maintain services for the NICNAME/WHOIS protocol on TCP/43. This is achieved by using a proxy service to translate traditional ARIN Whois queries into Whois-RWS queries.

My parser broke. Why did you change the NICNAME/WHOIS port 43 output?

In July 2010, ARIN made minor changes to the output for clarity and better adherence to the existing Whois help documentation. In March 2011, ARIN made improvements to DNS that allow finer control of DNS delegations. This resulted in adding delegation queries to the Whois-RWS system, including port 43. ARIN recommends that you use the RESTful interface for a more stable and easily automated set of queries/results.

The results of my network, IP and CIDR queries no longer include nameserver information. What happened?

In March 2011, ARIN made improvements to DNS that allow finer control of DNS delegations. Delegation queries were added to the Whois-RWS system, including port 43. Nameservers and DNS DS record information now appear in delegation query results. Please reference the Whois-RWS API documentation for information on constructing these queries.

How do I use the ARIN Whois RESTful Web Service?

Several websites offer a lot of general documentation about RESTful services. Use your favorite search engine to find how-to documentation. For specifics about using ARIN’s RESTful service, please read our Whois-RWS API Documentation.

My RESTful queries return hard-to-read xml. How do I make the output easier to understand?

Try submitting the query using the Firefox web browser; it will reformat that data and present it in a more readable form. The Data Formats section of the Whois-RWS API documentation describes several other methods to reformat data outputs.

Can I see the schemas for ARIN’s Whois-RWS?

Yes. The schemas are available on the ARIN website.

Should I change my code to parse the RESTful Interface instead of the NICNAME/WHOIS TCP port 43 service?

Absolutely. We encourage use of the new RESTful service for the purposes of programmatic consumption. ARIN plans to make more features available on the RESTful interface. The NICNAME/WHOIS service will remain accessible, but it may not support the enhanced features we intend to incorporate within Whois-RWS.

Where do I find clients that utilize Whois-RWS?

ARIN’s web interface is an example client, as are most web browsers. ARIN has also developed a set of command line scripts called ARINcli, written in Ruby, that utilize both Whois-RWS and ARIN’s Registration RESTful Web Service (Reg-RWS), and are available on Another Whois-RWS client has been developed by the community for use with Microsoft’s .NET framework, and is available via a link on or on GitHub.

Is your code open source?

For the server, the code is specific to ARIN and matches our database closely.  We do not believe this code is very useful to the community.  If we do see demand, ARIN may develop or assist some motivated individual/organization to create a generic open source implementation.

On the client side, the RESTful interface has created a rich framework for application developers. We hope that people leverage this framework and contribute code. To that end, ARIN has created an open-source repository.

Is ARIN’s RESTful provisioning service the same thing as ARIN’s RESTful Whois service?

No. They are separate services that utilize the same web framework.  Expect to see more information on this alternative to submitting templates soon. Find out more about ARIN’s RESTful provisioning service.

How do I find the parent/children networks of a network?

Please read the IP Addresses and Networks section of the Whois-RWS API documentation. The examples show how to use the more or less operator. The less operator allows you to see the supernets (or parent networks) while the more operator allows you to see the subnets (or children networks) of a particular network.

Where do I find more information on RESTful web services in general?

Use your favorite search engine to find information on REST. Several sites do a good job describing RESTful web services, how to create them, and how to utilize them. An excellent tutorial on this subject is available from O’Reilly publishing: RESTful Web Services by Leonard Richardson and Sam Ruby.

How Can I Test Whois-RWS Interactions?

ARIN has implemented an Operational Test and Evaluation environment (OT&E) containing a copy of production-like data, refreshed monthly, that allows developers to experiment with ARIN interactions like Whois-RWS. For more information, see the OT&E page.