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Domain Name Whois

Learn how to find out domain name registration using the WHOIS tool.

Conducting a WHOIS lookup can help determine ownership of Web site domain names. [©Jupiter Images, 2009]
©Jupiter Images, 2009
Conducting a WHOIS lookup can help determine ownership of Web site domain names.

WHOIS lookups are one of the most efficient ways to dig up ownership information about Internet domain names. Yet even though the service has existed since the 1980s, many Web users still don't know what it is or how to use it. This article answers basic questions on how the WHOIS protocol works, who maintains the WHOIS service, and how to efficiently locate and operate it for business or personal use.

What is WHOIS?

WHOIS (not an acronym) is a protocol -- a set of rules for communication between two computers -- that can be used to determine the owner of an Internet domain name or an IP address. The service was first made available in the 1980s shortly after the Internet began to take its current form. In those days, users could even search by last name to find out who had registered domain names. Since then, the search function has become less permissive.

WHOIS works by querying an official database of registry information and can be used for a number of different purposes. For example, many use WHOIS to find out which domain names are available for purchase. It's also helpful to law enforcement agencies for combating various Internet crimes, including fraud and illegal pornography.

Where to Find WHOIS Information

Many sites offer WHOIS lookups, but the most user-friendly is probably WHOIS.net, which maintains nearly 100 million domains in its database. You can also use the site to register a domain for yourself or to search through the available domains in the WHOIS database. Another feature allows you to check out your own WHOIS information from your IP address, which the server looks up automatically.

Other WHOIS lookups are provided by Network Solutions and Better WHOIS, which claims to conduct searches across many different domain name registrars and also allows users to receive reports via e-mail. A comprehensive list of WHOIS lookups on many different sites can be found at the Open Directory Project, a human-edited directory of the entire Web. This listing contains descriptions of the unique functions each WHOIS lookup performs, and which ones are more reliable or useful than others.


ARIN, the American Registry for Internet Numbers, is one of the world's five Regional Internet Registries (RIR). RIR are non-profit corporations that allocate IP addresses and maintain a registry database. Each one handles a certain region of the world, and ARIN's territory is the United States, Canada and a number of Caribbean islands. Every RIR also has a WHOIS server, so when users look up an IP address based in the United States, the information they get back is probably from ARIN.

The ARIN Web site provides its own WHOIS lookup, which browses all IP addresses contained in its database; for Web sites registered in the United States, this WHOIS service is one of the most reliable. A good starting point for searching for foreign Web sites, however, is to find out which RIR supervises registration for the region where the Web site is based, and then search that RIR's particular WHOIS service.

WHOIS Scripts Free

WHOIS scripts are available for download on the Internet in computer programming languages such as PHP or Perl. It's not a copyrighted service, so anyone is free to edit the protocol for their own purposes. These scripts are useful for programmers because they're easily edited for placement on a Web site or for personal use. By editing your own WHOIS script you can control what types of domains it searches for and how the interface works.

WHOIS lookups can also be edited to search domains in different languages, privilege some results over others or search within one or all directories. Writing your own WHOIS lookup, if you've got the programming skills, also ensures that you know the quality of results you're getting back when you search. Don't worry if you're not that proficient with computers. Just about any search can be executed by one WHOIS lookup or another.

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