Credentialled RDAP

As part of the standardisation of the .UK registry, the existing List APIs (REST and SOAP) are being retired and replaced by Credentialled RDAP.

RDAP (Registration Data Access Protocol) is an internationally recognised standard for retrieving domain registration data. It is defined by the IETF and adopted across registries and registrars globally. Unlike proprietary APIs, RDAP provides a consistent, structured, and extensible way to access domain data.

Credentialled RDAP makes use of the standard and authentication of users to access data where permitted.

Why RDAP

The move to RDAP introduces a number of structural improvements over the previous List APIs:

Standardised format
RDAP responses follow a globally defined structure. This reduces the need for registry-specific integrations and simplifies long-term maintenance.
Consistency across registries
The same protocol is used across multiple TLDs and providers, allowing for more portable tooling and integrations.
Rich, structured responses
RDAP returns a full representation of a domain object, including events (such as creation and expiry), nameservers, and associated entities (e.g. registrant details).
Extensibility
The model allows additional fields and capabilities to be introduced without breaking existing integrations.
Future alignment
RDAP is the direction of travel across the domain industry, including ICANN gTLD registries, making it a more sustainable integration point.

Key Difference from List APIs

The List APIs were primarily query-based: you requested a specific dataset (e.g. domains by expiry date) and received a filtered list.

RDAP works differently.

RDAP returns structured domain data. Instead of calling different endpoints for each type of query, you retrieve domain data and then use the fields within the response to perform filtering, aggregation, or analysis on your side.

This means:

Fewer specialised endpoints
More flexibility in how data is used
Greater control for you to build your own queries and views

Working with RDAP Responses

A typical Credentialled RDAP response for domains by registrar is reduced RDAP response only including the following elements:

Domain name
Registration date
Expiry date
Domain ROID

These fields allow you to recreate many of the use cases previously supported by the List APIs.

Recreating Common Use Cases

While RDAP does not provide direct “list endpoints” for each query type, the response data contains the necessary fields to support similar outcomes.

Examples include:

Retrieve all domains

You can retrieve domain data via:

<registry>/registrar/domains

The response will include a list of domain objects (domainSearchResults).

For .UK testbed the end query is https://testbed-rdap.nominet.uk/uk/registrar/domains

Domains by creation date

Each domain includes event data:

eventAction = registration
eventDate = <timestamp>

You can filter domains client-side based on the registration date to produce:

Domains created after a date
Domains created before a date
Domains within a date range

Domains by expiry date

Each domain includes:

eventAction = expiration
eventDate = <timestamp>

You can use this to derive:

Domains expiring after a date
Domains expiring before a date
Domains within an expiry range

Domains by nameserver

Nameserver data is included within each domain:

nameservers[].ldhName

You can filter domains by matching the nameserver value.

Contact and Entity Data

Where available, RDAP responses include entity information using a standard vCard structure:

Email
Organisation name
Address fields
Telephone

These are provided under:

entities[].vcardArray

This structure is standardised across RDAP implementations.

Sample query

curl -H “Authorization: Bearer ACCREDITATION123:ExampleAPIKEY1234” \
https://testbed-rdap.nominet.uk/uk/registrar/domains

Sample response

{
  "rdapConformance": [
    "subsetting",
    "rdap_level_0",
    "nominet_profile_0",
  ],
  "domainSearchResults": [
    {
      "objectClassName": "domain",
      "links": [
        {
          "value": "https://testbed-rdap.nominet.uk/uk/domain/example.uk",
          "rel": "self",
          "href": "https://testbed-rdap.nominet.uk/uk/domain/example.uk",
          "type": "application/rdap+json"
        }
      ],
      "events": [
        {
          "eventAction": "registration",
          "eventActor": "NOMINET",
          "eventDate": "2018-12-12T10:48:51.326Z"
        },
        {
          "eventAction": "last changed",
          "eventActor": "NOMINET",
          "eventDate": "2025-12-07T23:06:58Z"
        },
        {
          "eventAction": "expiration",
          "eventDate": "2026-12-12T10:48:51.326Z"
        }
      ],
      "handle": "D_00D08A42_7B99433C897C482996BE92708E1EC811_00000167A2089781-UK",
      "ldhName": "example.uk"
    },
    {
      "objectClassName": "domain",
      "links": [
        {
          "value": "https://testbed-rdap.nominet.uk/uk/domain/nominet.uk",
          "rel": "self",
          "href": "https://testbed-rdap.nominet.uk/uk/domain/nominet.uk",
          "type": "application/rdap+json"
        }
      ],
      "events": [
        {
          "eventAction": "registration",
          "eventActor": "NOMINET",
          "eventDate": "2019-09-03T09:44:24.912Z"
        },
        {
          "eventAction": "last changed",
          "eventActor": "NOMINET",
          "eventDate": "2025-08-29T23:08:02Z"
        },
        {
          "eventAction": "expiration",
          "eventDate": "2026-09-03T09:44:24.912Z"
        }
      ],
      "handle": "D_01321C19_357CE30559DE4F0F85C89A1B091F3059_0000016CF682D452-UK",
      "ldhName": "nominet.uk"
    }
  ],
  "notices": [
    {
      "title": "Terms of Service",
      "description": [
        "The Registration Data Access Protocol (RDAP) service provides access to the records in the RDAP database for information purposes only, to assist you in obtaining information about the registration records of existing domain names. The stored information in the RDAP database is provided as is. We do not guarantee its accuracy or completeness, and cannot be held liable if the stored information in the RDAP database is wrong, incomplete, or inaccurate in any way. By querying the RDAP database in any way, you agree that you will not use this data: (i) to allow, enable or otherwise support the transmission of unsolicited, commercial advertising or other solicitations in any form or by any means; (ii) to enable high volume, automated, electronic processes that query or send data to the Registry Operator or registrar or registrant; (iii) for target advertising; (iv) to cause nuisance to registrants by sending (by any means) messages to or contacting them; (v) to violate any law, rule, regulation or statute; and/or (vi) in violation of applicable data and privacy protection acts. You are explicitly prohibited from extracting, copying and/or using or re-using in any form and by any means (electronically or not) all or part (quantitatively or qualitatively) of the contents of the RDAP database without prior and explicit permission from the RDAP server owner. Any copying or transmission of data for commercial purposes violates this prohibition. You agree that we can take measures to limit the use of the RDAP service to protect the privacy of registrants or the integrity of the database. We reserve the right to make changes to this website, the RDAP service, and these Terms and Conditions at any time without prior notice to you. You should review these Terms and Conditions each time you access or use the RDAP database and the RDAP service to learn of any changes. If you do not agree to the changes we have made, your only remedy is to stop your use of the RDAP database and the RDAP service. By executing a query, in any means whatsoever, you agree to these Terms of Service."
      ],
      "links": [
        {
          "value": "https://new-rdap.testbed.dev.registry.nominet.cloud/wales/registrar/domains",
          "rel": "terms-of-service",
          "href": "https://nominet.uk/rdap-tos",
          "type": "text/html"
        }
      ]
    }
  ],
  "subsetting_metadata": {
    "currentFieldSet": "brief"
  }
}

Accessing Credentialled RDAP

To access credentialled RDAP you need an API Key. If you are already an existing user of the SOAP or REST API, your old key will be accepted. If you need a new one, follow the steps below:

Generate Your API Keys

Log into Online Services: https://secure.nominet.org.uk/auth/login.html .
Navigate to Account Settings.
Navigate to the section: Credentialled RDAP API.
Select the environment (Live or Testbed) and the accreditation you wish to generate an API key for.
To generate API Keys, click Generate.
Keys will be generated. Make a note of these, as you can only view them when you generate them.
If you need a new API key, click regenerate and make a note of the new key. This will overwrite any previously generated keys for the selected accreditation and environment.

Rate Limiting

To provide a balanced and performant experience for all users, we are introducing specific throughput and pagination parameters:

Feature: Reduced RDAP responses with Pagination.
Page Size: Search results are delivered in segments of 50 results per page.
Rate Limiting: To ensure service stability, API access is limited to one response per second.
Benefit: These measures prevent system timeouts and allow for predictable, progressive retrieval of large domain sets.

Adjustment to Date-Based Filtering

We previously communicated the intent to implement server-side date-based filtering (e.g., registration and expiry dates). Following a review of current usage and development priorities, we have made the following adjustments:

Current Status: Server-side filtering for registration and expiry dates will not be implemented at this time.
Alternative Approach: Date fields (registration and expiry) will remain fully present in all RDAP responses. Registrars can retrieve this data and perform any necessary filtering or sorting on their own systems (client-side).
Rationale: This decision ensures we remain aligned with global RDAP standards while prioritising core service stability.
Future Outlook: We will continue to monitor member requirements. If a significant volume of requests for server-side filtering is raised by our registrar community, we may reconsider this feature for future development roadmaps. Feedback can be supplied via uservoice here.

Please note: Credentialled RDAP is only available on Nominet’s Registry Services Platform and therefore the production .UK registry will only be supported from the date of transition.

Nominet

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