Introduction

client.rdap.org is a web-based tool that allows you to perform WHOIS-like lookups for domain names using the RDAP (Registration Data Access Protocol). RDAP is the modern successor to the traditional WHOIS protocol, providing data in a standardized, machine-readable format.

How to Use It

Using client.rdap.org is straightforward:

1. Open your web browser and navigate to client.rdap.org.
2. Enter the domain name you want to query into the search bar at the top of the page.
3. Decide which record you want:
   • Registry Record (Default): If you want the information from the TLD registry (e.g., the operator of .com or .org), simply click the "Submit" button.
   • Registrar Record: If you want to get the information from the domain's registrar (the company where the domain was registered), check the box labeled "Follow referral to registrar's RDAP record" before clicking "Submit."
4. Review the results displayed on the page.

How It Works

When you submit a domain name:

1. client.rdap.org first determines the authoritative RDAP server for the TLD of the domain you entered. It uses information (often called a "bootstrap service" or a list of RDAP server locations) based on data maintained by IANA (Internet Assigned Numbers Authority).
2. By default (without the checkbox): The tool sends an RDAP query to the registry's RDAP server for that TLD. The registry returns information about the domain.
3. With the "Follow referral..." checkbox ticked: The tool first queries the registry. The registry's response often includes a "referral" or link to the sponsoring registrar's RDAP server. The tool then automatically follows this link and queries the registrar's RDAP server for its version of the domain's information.
4. The data received is in JSON format (a structured way of representing data). client.rdap.org then parses this JSON and displays it in a more human-readable format. You can usually find an option to view the raw JSON output at the bottom of the results page.

Why query both Registry and Registrar?

In theory, the registration data held by the registry and the registrar should be synchronized. However, discrepancies can sometimes occur. If you're investigating a domain in detail, it's often a good idea to query both and compare the results. Differences might indicate:

• The domain is undergoing a transfer to a different registrar.
• Recent updates haven't fully propagated or synchronized.
• The domain was recently deleted or is in a pending state.
• A potential technical issue at the registry or registrar level.

Reading the Results

The results page typically presents information in distinct sections. Here are some common fields you might encounter and what they mean:

Field	Description
Object Class Name	Usually "domain" for a domain lookup.
Handle	A unique identifier for the domain record, often specific to the registry or registrar (e.g., "Domain Name" in some outputs).
LDH Name	The "Letter-Digit-Hyphen" name, which is the domain name itself (e.g., example.com).
Events	Key dates associated with the domain. Common events include: registration (creation date), expiration date, last changed date, and last update of RDAP database.
Status	An array of status codes applicable to the domain. These are EPP status codes (e.g., clientTransferProhibited, ok). For more details, see ICANN EPP Status Codes.
SecureDNS (DNSSEC)	Information about DNSSEC (Domain Name System Security Extensions) if it's enabled for the domain, such as delegationSigned (true/false) and details about DS records.
Nameservers	The authoritative nameservers for the domain.
Entities	Information about organizations or contacts associated with the domain. Due to privacy regulations like GDPR, this is often limited to the registrar and abuse contacts.
Within an Entity:
Handle (Entity)	A unique identifier for the entity (e.g., the registrar's ID).
Roles	The function of the entity concerning this domain (e.g., registrar, abuse).
Public IDs (Entity)	May contain identifiers like the IANA Registrar ID.
vCard (Entity)	Contact information for the entity, often including the organization's name and sometimes an address or email for abuse reporting.
Notices	Any legal disclaimers, terms of service, or other informational messages from the RDAP server provider (registry or registrar).
Links	URLs related to the query, such as a link to the RDAP server itself (self link) or links to related resources.
RDAP Conformance	Indicates the RDAP specifications and ICANN policies that the response aims to conform to.

Each section in the human-readable output on client.rdap.org often has a button or link to "show raw output." This reveals the underlying JSON field from which the displayed data was extracted, which is very helpful for understanding the raw RDAP structure.

Strengths

• Standardized Output: Uses RDAP, providing more consistent and machine-readable (JSON) data compared to traditional WHOIS.
• User-Friendly Interface: client.rdap.org does a good job of presenting complex JSON data in an easier-to-understand format.
• Direct Registry/Registrar Queries: Allows specific targeting of either the registry or registrar data.
• Reflects Modern Privacy Norms: By default, RDAP responses for gTLDs will redact PII (Personally Identifiable Information) for registrants, aligning with GDPR and current ICANN policies.

Limitations

• Rate Limiting: Like many public lookup tools, queries from your IP address might be rate-limited if you perform too many in a short period.
• Current Data Only: The results reflect the current state of the domain's registration data at the time of the query. It's a snapshot, not a historical record.
• Limited Registrant PII: Consistent with privacy regulations, you generally won't find detailed personal registrant information (name, address, direct email of the individual) in public RDAP responses for many domains, especially gTLDs. You'll typically see registrar and sometimes abuse contact information.
• ccTLD Support Varies: While RDAP is mandated for gTLDs, its adoption and the richness of data provided by ccTLD (country-code Top-Level Domain) registries can vary. client.rdap.org's ability to query ccTLDs depends on whether the ccTLD's RDAP service is discoverable via standard mechanisms.