RDAP is the successor to the current whois protocol. The service is currently under development at many registries, and at Norid as well.
The service is available at:
The service is a prototype. As the service is still in the development stage, changes to the format for lookups and responses must be expected.
The service is available at:
RDAP is considered to be the successor to the current whois protocol and includes a number of improvements compared to this protocol.
- The transfer format for lookup data is clearly specified as JSON format, and is easy to process automatically.
- Character sets are uniquely specified.
- The protocol offers the option of so-called ‘layered access’. This means that privileged users can be authenticated and gain access to more data compared to anonymous users. This could include more detailed data or a larger lookup rate.
How the service works
The service is available at the following URL:
The service supports lookups of domain names, contact data (entities) and name servers. Some examples:
Domain name lookup:
Lookup of contact person with personal handle as the key:
Lookup of domain provider with provider ID as the key:
Lookup of name server with name server handle as the key:
Search for name server with a certain host name:
RDAP is designed as a web service. Queries are submitted as URLs, to which the server responds with data in JSON format. RDAP uses the HTTP method GET to look up data on an object. The HTTP method HEAD is used to submit a query for whether an object exists.
Data for an object (domain name, contact or name server) can be looked up using the HTTP method GET. This is equivalent to a lookup in the whois protocol. The response to the lookup is the return code 200 OK and a set of JSON data if the object exists, and 404 Not Found if it does not.
Query for whether an object exists
A query for whether an object (domain name, contact or name server) is registered is submitted using the HTTP method HEAD. This is equivalent to a lookup in the DAS protocol. The query returns the return code 200 OK if the object exists, and 404 Not Found if it does not
The RDAP protocol is an international standard, but it allows local extensions and adjustments. Norid’s RDAP server has a local extension that enables lookups of name servers based on name server handles. Please note that this extension does not change the behaviour or return data for any of the other standardized queries. A general RDAP client should therefore be able to handle standardized queries without any compatibility issues.
Extension for looking up name servers
The standard lookup for name server objects use name server host names as the lookup key. In Norid’s registration system, name server lookups keyed to host names will not be unique, as the system may contain several name server objects with the same host name. We have therefore chosen to offer a separate lookup for name servers based on name server handles:
These lookups will return a data object formatted the same way as standard RDAP lookups for name servers.
The RDAP service has two rate limits — both limit the number of lookups made from any given IP address. One rate limit allows a maximum of 300 GET queries from any one IP address and 3000 HEAD queries per 24 hours in a sliding window. The other rate limit allows each IP address access to a maximum of 10 lookups (GET or HEAD) per minute. If either of these limits is exceeded, lookups will return 429 Too many requests.
Software for RDAP clients
RDAP is a web service, so any web browser can, in principle, be used as an RDAP client, as long as it is capable of receiving and presenting JSON data. Command-line clients, such as wget and curl, can be used to retrieve data for scripting:
There are other, more specialized clients that can present JSON data in a more readable way. The following clients are available in open source code:
OpenRDAP - command line client written in Go.
NicInfo - command line client written in Ruby.
A detailed description of how the service works can be found in the RFC specifications for the RDAP protocol: