Understanding Whois for Developers

Understanding Whois for Developers

As a developer, you must have heard about Whois, a domain registration lookup tool for the internet. Whois is a protocol used to query databases that contain information about internet resources, including domain names, IP addresses, autonomous system numbers, and other network resources. In this article, we will explain the concept and usage of Whois in Internet and network security for developers.

What is Whois?

Whois is a protocol that helps to retrieve and display information about domain registration details. The information provided includes the name and contact information of the domain owner, the domain’s registration and expiration date, and the name and contact information of the domain registrar. Whois queries can also be used to determine if a domain name is available for registration, its current status, and historical ownership details.

Whois queries are executed using a Whois client or tool. Typically, the client sends a query to a Whois server that contains the requested information. The server then sends the data back to the client in either plain text or structured format.

How to use Whois?

There are many ways to use Whois. You can use the command-line tool in Linux or macOS by running the whois command followed by the domain name or IP address. For example, to query the domain registration information for the domain example.com, run the following command:

whois example.com

Or you can use Whois tool in He3 Toolbox (https://t.he3app.com?9hgh ) easily.


Scenarios for developers

As a developer, you can use Whois to perform various tasks, such as:

  • Check if a domain name is available for registration
  • Retrieve domain registration details and verify ownership
  • Troubleshoot network issues by identifying IP address ownership and contact information
  • Monitor domain name changes and expiration dates
  • Detect potential trademark infringement or cybersquatting

Key features of Whois

Whois provides various features that make it useful for Internet and network security, including:

Domain registration lookupRetrieve domain name registration information and details
IP address lookupIdentify the ownership and ownership history of an IP address
Autonomus System (AS) number lookupObtain information about an AS number and its associated routes
Contact information retrievalLocate contact information for domain owners and technical contacts
Information validationVerify the accuracy and reliability of registration and contact information

Misconceptions about Whois

There are some misconceptions about Whois that need to be clarified:

Whois is a directory for all domains

This is not true. Whois is a protocol that provides access to domain registration information. Not all domains are registered in a Whois database, and some might have hidden registration details.

Whois provides personal information about domain owners

Whois provides only public information about domain registration, which includes the name, address, and contact information of the domain owner. This information is required by domain registrars to comply with the Internet Corporation for Assigned Names and Numbers (ICANN) guidelines.


Is Whois free to use?

Yes, Whois is free to use. However, some domain registrars and Whois servers might have usage restrictions or require authentication.

How accurate is the information provided by Whois?

The accuracy of Whois information depends on the correctness of the registration and contact information provided by the domain owner. Some domain owners might provide false or incomplete information, which can affect the accuracy of Whois.

Can I use Whois to find the IP address of a website?

Yes, you can use Whois to find the IP address of a website. However, you can also use other tools, such as ping or nslookup, to retrieve the IP address.


Whois is an essential tool for Internet and network security. As a developer, you can use Whois to perform various tasks related to domain registration and IP address ownership. Remember that Whois provides only public information about domain registration, and some domains might have hidden registration details. To learn more about Whois, visit the Wikipedia page or the ICANN website.