What Is RDAP?

RDAP, or the Registration Data Access Protocol, is a modern protocol used to retrieve registration information about internet resources such as domain names, IP address ranges, and autonomous system numbers.

It was designed to provide a more structured and standardized alternative to the traditional WHOIS system.

Quick answer: RDAP is a web-based protocol for looking up registration data about domains, IP networks, and ASNs. It returns structured data and provides a more modern foundation than the older WHOIS protocol.

What does RDAP stand for?

RDAP stands for Registration Data Access Protocol.

It is used to query registration databases that contain information about internet resources.

Depending on the resource being queried, RDAP may provide information about:

• domain names,
• IP address allocations,
• network ranges,
• autonomous system numbers,
• registrars or registries,
• registration events,
• and associated entities or contacts when that data is available.

Why was RDAP created?

For many years, WHOIS was the standard method for retrieving registration information.

WHOIS remains familiar to many network administrators and domain owners, but its output is largely plain text and can vary significantly between servers.

RDAP was designed to improve this situation by providing:

• structured responses,
• consistent data formats,
• web-based access,
• internationalization support,
• better support for access control,
• and easier machine processing.

How does RDAP work?

RDAP uses HTTP or HTTPS, the same basic web technologies used by browsers and APIs.

A client sends a request to an RDAP service for a particular internet resource. The server returns structured data, usually in JSON format.

A simplified process looks like this:

1. A user or application submits a domain, IP address, or ASN.
2. The appropriate RDAP service is identified.
3. A request is sent to that service.
4. The server returns structured registration information.
5. The application presents the relevant data to the user.

What kind of information can RDAP return?

The exact response depends on the type of resource and the policies of the registry or service providing the data.

An RDAP response may contain information such as:

• resource handle or identifier,
• domain or network name,
• registration status,
• creation or update events,
• registrar information,
• name servers,
• IP network start and end addresses,
• country or regional information,
• autonomous system information,
• related entities,
• and links to additional registration resources.

RDAP vs WHOIS

RDAP and WHOIS serve similar purposes, but they operate differently.

Feature	RDAP	WHOIS
Transport	HTTP / HTTPS	Traditional WHOIS protocol
Response format	Structured JSON	Mostly plain text
Machine processing	Easier	More difficult because formats vary
Standardized fields	Yes	Limited
Internationalization	Better support	More limited
Access-control support	Built into the protocol design	Less standardized

Why is structured JSON useful?

One of RDAP's major advantages is that the response follows a structured data format.

Applications do not have to guess where a piece of information appears in a block of text.

Instead, software can identify fields such as:

• network start address,
• network end address,
• status,
• events,
• entities,
• and links.

This makes RDAP especially useful for automated network tools and APIs.

Can RDAP look up IP addresses?

Yes.

RDAP can be used to retrieve registration information associated with an IP address or network range.

For example, an IP RDAP lookup may reveal:

• the allocated network range,
• the organization associated with the allocation,
• the relevant regional registry,
• registration status,
• and related registration records.

This should not be confused with IP geolocation.

RDAP describes registration and allocation information, while geolocation services attempt to estimate where an IP address is being used.

Can RDAP look up domain names?

Yes.

For supported domain registries, RDAP can provide registration information about a domain.

Depending on the registry and privacy policies, this may include:

• domain status,
• registrar information,
• name servers,
• registration dates,
• expiration-related events,
• and links to related records.

Can RDAP look up an ASN?

Yes.

RDAP can also retrieve information about an Autonomous System Number (ASN).

An ASN identifies an autonomous system participating in internet routing.

An ASN RDAP response may contain information about:

• the ASN or range of ASNs,
• the organization associated with the resource,
• registration status,
• events,
• and related entities.

Who operates RDAP services?

Registration data for internet resources is distributed among different registries and authorities.

IP addresses and autonomous system numbers are commonly associated with the regional internet registry responsible for the allocation.

Domain registration data is provided through the registry or RDAP service responsible for the relevant domain namespace.

What are Regional Internet Registries?

Regional Internet Registries, often abbreviated as RIRs, manage the allocation and registration of IP address resources and ASNs within different parts of the world.

The five RIRs are:

• AFRINIC — Africa
• APNIC — Asia-Pacific
• ARIN — Canada, the United States, and parts of the Caribbean
• LACNIC — Latin America and parts of the Caribbean
• RIPE NCC — Europe, the Middle East, and parts of Central Asia

An RDAP client can use the appropriate registry service to retrieve information about IP and ASN resources.

How does RDAP know which server to query?

Different organizations are responsible for different internet resources.

RDAP clients can use bootstrap information to determine which RDAP service is authoritative for a particular domain, IP range, or ASN.

This makes it possible for software to direct a query to the appropriate registration data service automatically.

What is an RDAP bootstrap service?

A bootstrap system helps map an internet resource to the RDAP service that should be queried.

For example, an IP address belongs to a particular allocation hierarchy. Bootstrap information helps the client determine which regional registry should receive the request.

What does an RDAP response look like?

RDAP normally returns JSON data.

A simplified response might contain fields conceptually similar to:

{
  "handle": "EXAMPLE-NET",
  "startAddress": "203.0.113.0",
  "endAddress": "203.0.113.255",
  "status": ["active"],
  "events": [
    {
      "eventAction": "registration"
    }
  ]
}

Real RDAP responses can contain substantially more information.

What are RDAP entities?

RDAP uses entities to represent organizations, registrars, contacts, or other parties associated with a registration record.

An entity may have one or more roles, such as:

• registrant,
• registrar,
• administrative contact,
• technical contact,
• or abuse contact.

The information actually displayed can vary because of registry policies, privacy rules, and access restrictions.

Why might some RDAP information be hidden?

Registration systems do not necessarily expose every stored field publicly.

Some information may be:

• redacted,
• restricted,
• available only to authenticated users,
• or omitted because of privacy and data-protection policies.

Therefore, an RDAP lookup should not be expected to reveal the personal identity of every domain owner or network user.

Does RDAP reveal who is using an IP address?

Not necessarily.

RDAP normally describes the organization or network resource associated with an IP allocation.

It does not automatically identify the individual person who happens to be using that address at a particular moment.

For residential internet connections, the registration record may point to an internet provider rather than an individual customer.

RDAP vs IP geolocation

These tools answer different questions.

RDAP	IP Geolocation
Registration and allocation data	Estimated geographic information
May identify a network organization	May estimate country, region, or city
Based on registry records	Based on geolocation datasets and network observations

RDAP vs DNS

RDAP and DNS also serve different purposes.

DNS helps translate names into network information needed to reach internet services.

RDAP retrieves registration information associated with internet resources.

For example:

• DNS may tell you which IP address a hostname uses.
• RDAP may tell you which organization holds the registration for that IP range.

Is RDAP only for technical users?

No.

Network administrators, security teams, researchers, domain owners, developers, and ordinary users can all benefit from RDAP information.

Common uses include:

• investigating an unfamiliar IP address,
• checking domain registration information,
• identifying the registry responsible for an address range,
• researching an ASN,
• network troubleshooting,
• and understanding internet resource ownership.

Can RDAP be used automatically?

Yes.

RDAP is particularly suitable for software and automated tools because its responses are structured.

Developers can retrieve JSON data and process individual fields without having to parse inconsistent plain-text WHOIS output.

Is RDAP a search engine?

No.

RDAP is a protocol for retrieving registration data from services responsible for internet resources.

A website or application may provide an RDAP search interface, but RDAP itself is the underlying protocol used to retrieve the information.

How can I perform an RDAP lookup?

IPScope includes an RDAP lookup tool inside the Network Toolbox .

Enter a supported domain name or IP address and run the lookup to retrieve available registration information.

The exact fields returned depend on the resource and the RDAP service responsible for it.

When is an RDAP lookup useful?

An RDAP lookup can be useful when you want to:

• identify who manages an IP allocation,
• inspect a registered network range,
• check domain registration status,
• review registrar information,
• find registration dates or events,
• research an autonomous system,
• or investigate network ownership.

Does RDAP replace WHOIS?

RDAP was designed as the modern successor to traditional WHOIS for registration data access.

WHOIS may still be encountered and remains familiar to many users, but RDAP provides a more standardized framework for modern applications and internet registration services.

Key takeaway

RDAP is a modern protocol for retrieving registration information about domains, IP networks, and autonomous system numbers. It provides structured JSON responses over web protocols and offers a more standardized foundation than traditional WHOIS.

Related IP & network guides

To understand the network addresses that can be queried through RDAP, read What Is an IP Address? .

For IPv4 and IPv6 differences, see IPv4 vs IPv6 .

To understand domain name resolution, read What Is DNS? .

To inspect your current public network address, see How to Check Your Public IP .