Whois is a service that allows retrieving information about the owners of addresses on the Internet (domains) and IP addresses. The English phrase "Who is" translates to "who is it" - searchers get information about domain names and IP addresses.
In order to get deposited information, the knowledge of the corresponding whois server is necessary depending on the domain. Unfortunately, the queries themselves are becoming more and more expensive due to the new endings for different countries and the new generic top level domains.

With WHOIS you can read information about domains and IP addresses. All that is required is the knowledge of the corresponding whois server. If you do not want to deal with the technical details, you can start the request via the numerous providers for web-based domain lookups. In many operating systems, the information can also be retrieved from the command line by simply typing whois example.com .

The obtained details about top-level domain can differ. But in general, the information concerns the domain owner, administrative contact, technical contact, zone administrator and the name servers. Name servers translate the complex IP address into the easy to remember domain and domain extension.

The obtained information may, however, be used only in certain cases. For example, it is prohibited to send spam to the received email addresses. It is explicitly allowed to establish contact in case of technical issues, infringement of rights of third parties or other problems with the domain or IP address.

The possibilities for using WHOIS differ depending on the administrative body. You and the five global administrators of IP addresses offer different ways to read public information about a domain or IP address.
The whois information is maintained by the respective registries such as nic.at for .at domains , the Internet Corporation for Assigned Names and Numbers (ICANN) for all generic and new top levels Domains and the Regional Internet Registrys for the IP addresses. Different versions of the whois service are used. Basically, the information that can be read out via the whois query differs. Each registry has slightly different rules for managing the information.

A WHOIS query is often the only way to get to the data of the domain owner in the absence of imprint. This is interesting in very different situations. The service is designed to give third parties the ability to contact directly on issues. For example, if the content on the domain violates the rights of third parties, it is possible to contact the person in charge.
Another conceivable case is that the domain poses a technical threat. Especially important is the service for anyone whose rights are violated by the domain . In times of cyber-bullying, this is a ray of hope for many victims who are to be defamed on a website without an imprint.

The first point of contact for domains is always the domain holder stored in the WHOIS data. Should this not respond to the contact, it is also possible to contact directly the administrative contact, the technical contact person or zone administrator and to inform them about the infringement. This ensures that legal violations or problems can be eliminated in a timely manner.
Different data will be provided depending on the registrar. For example, for .de domains , only name and address are stored by default. So the first contact usually has to be done by mail. Other registrars for top-level domains also have electronic contact information, which makes it easier to contact them by phone, fax or email.