---
title: WHOIS Protocol
description: Get an overview of WHOIS. Learn how this protocol is used to query databases for information about the registered user or assignees of a domain name.
---

import {LinkCard} from "@astrojs/starlight/components";

WHOIS is a text-based query/response protocol (listening on **TCP Port 43**) widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name or an IP address block.

## Core Use Cases

* **Availability Check**: Verifying if a specific domain name is available for registration.
* **Ownership Identification**: Identifying the Registrant or the Registrar managing the domain.
* **Technical Troubleshooting**: Finding the authoritative nameservers or the technical contacts to resolve network issues.
* **Legal & Abuse**: Providing a record for law enforcement, intellectual property protection, and abuse reporting.

## Thick vs. Thin Registries

Understanding WHOIS responses requires understanding how the TLD Registry stores data.

### Thin Registry (e.g., .com, .net)

The Registry only stores technical data (DNSSEC, Nameservers) and a pointer to the Registrar.

To get the full contact details, a second WHOIS query must be sent to the **Registrar's WHOIS server**.

### Thick Registry (e.g., .org, .info, most ccTLDs)

The Registry stores *all* information, including the Registrant's contact details and administrative data.

A single query to the Registry provides the full record.

## Example: Recursive WHOIS Query

The standard `whois` command line tool often handles the "Thin Registry" redirect automatically.
However, seeing the raw steps helps understand the protocol.

In the example below for a **Thin TLD** (`.com`), we first query the Registry, which points us to the Registrar.

### Request to the Registry (Verisign)

Note the `Registrar WHOIS Server` field in the response.

```text title="WHOIS query to the Registry"
$ whois --verbose example.com -h whois.verisign-grs.com.
Using server whois.verisign-grs.com..
Query string: "example.com"

   Domain Name: EXAMPLE.COM
   Registry Domain ID: 2336799_DOMAIN_COM-VRSN
   Registrar WHOIS Server: whois.iana.org
   Registrar URL: http://res-dom.iana.org
   Updated Date: 2025-08-14T07:01:39Z
   Creation Date: 1995-08-14T04:00:00Z
   Registry Expiry Date: 2026-08-13T04:00:00Z
   Registrar: RESERVED-Internet Assigned Numbers Authority
   Domain Status: clientDeleteProhibited https://icann.org/epp#clientDeleteProhibited
   Domain Status: clientTransferProhibited https://icann.org/epp#clientTransferProhibited
   Name Server: A.IANA-SERVERS.NET
   Name Server: B.IANA-SERVERS.NET
   DNSSEC: signedDelegation
>>> Last update of whois database: 2025-11-20T08:05:54Z <<<
```

### Request to the Registrar (IANA)

Following the referral, we query the specific Registrar to get the ownership details.

```text title="WHOIS query to the Registrar"
$ whois --verbose example.com -h whois.iana.org
Using server whois.iana.org..
Query string: "example.com"

% IANA WHOIS server
% for more information on IANA, visit http://www.iana.org
% This query returned 1 object

domain:       EXAMPLE.COM
organisation: Internet Assigned Numbers Authority
created:      1992-01-01
source:       IANA
```

## Privacy Considerations

Since the implementation of the **GDPR** (General Data Protection Regulation) and similar global privacy laws, the WHOIS output has changed significantly.

* **Data Redaction**: Most personal fields (Name, Email, Phone) are now replaced with placeholders like `DATA REDACTED` or `Redacted for Privacy`.
* **Privacy Proxies**: Registrars often provide services that replace the registrant's details with the registrar's generic contact information to prevent spam and harassment.
* **Tiered Access**: Full, unredacted data is often no longer publicly available anonymously and requires a legitimate legal request or accreditation.

<LinkCard title="RDAP Protocol" href="/en/definitions/rdap/"
          description="Learn about the successor to WHOIS designed to handle structured data and privacy access."/>

## See also

* [RFC 3912 - WHOIS Protocol Specification](https://datatracker.ietf.org/doc/html/rfc3912)
