RDAP
RDAP is the JSON-based successor to WHOIS. It returns registration data for IP ranges, ASNs, and domains from the registries themselves.
What RDAP is
The Registration Data Access Protocol is the modern replacement for the WHOIS protocol. Instead of a plain-text conversation on port 43 with a format that every registry invented for itself, RDAP is an HTTPS API that returns structured JSON. The same query works against every regional internet registry and every domain registry that supports it, and the answer has named fields: the network handle, its start and end address, the country, the holding organization, abuse contacts, and the dates it was allocated and last changed.
RDAP also solves the "which server do I ask?" problem. IANA publishes bootstrap files that map IP ranges, ASN ranges, and top-level domains to the responsible registry's RDAP endpoint. A client downloads those files, finds the matching entry, and sends its query to the right place.
Why it matters
For an IP address, RDAP tells you who holds the block and how large it is, which is the authoritative answer behind a hosting or ISP classification. The ASN record tells you who runs the network. For a domain, it shows the registrar, status codes, name servers, and whether DNSSEC is enabled. Because the data comes from the registry rather than a third-party copy, it is as current as the registry itself.
Registries redact personal data under privacy rules, so RDAP responses for domains often show the registrar and an abuse contact rather than the registrant's name. That is expected behavior, not an error.
How we use it
Our WHOIS tool is built on RDAP. We fetch the IANA bootstrap files and cache them for a week, send queries to the registry's HTTPS endpoint, and cache each result for 24 hours. The raw WHOIS protocol on port 43 is not used from the web server. The same normalized record is available in the API by adding ?whois=1 to an IP or ASN request.
How to check
Enter an IP address, a CIDR block, an ASN, or a domain in the WHOIS tool. IP lookup shows a registry summary for any address you query, and ASN lookup shows the registry record for a network.
A common misconception
RDAP and WHOIS contain the same underlying data. If a result looks different from a legacy WHOIS output, it is because RDAP presents the fields consistently and applies the registry's current redaction policy, not because one of them is wrong.