RDAP: who owns your domain and when it disappears
Whether you own your domain does not stand with your hosting or your registrar — it stands in the register of the registry of the TLD: SIDN for .nl, Verisign for .com, and hundreds of others each for their own extension. For thirty years you could knock there with WHOIS: free text over an open port, without rules about who asks what, and precisely therefore that channel became an increasing source of complaints.
RDAP is the successor: the same register, but as structured JSON over HTTPS, with ICANN-defined status codes, events with fixed names and privacy decisions that the registry names openly in its answer instead of behind the curtains. One thing stayed the same: the data does not stand with us but with the registry — and then you must know which registry.
That knowing is what the RDAP domain lookup does: the map of IANA decides which registry belongs to your TLD, our server asks exactly that registry, and the answer — registrar, status, expiry date, nameservers and DS keys — is drawn out. This article reads that answer field by field.
1. From WHOIS to RDAP
WHOIS asked on port 43, in plain text, with each registry its own format, its own rate limits and its own gradation of openness. That is what made WHOIS famous — and with it also an easy target: scraping machines collected contact details en masse, on which GDPR and the registries themselves took more and more back. A format that cannot carry a status code cannot carry policy either.
RDAP (RFC 7483 and surroundings) asks the same registries over HTTPS and answers in JSON: objectClassName, events with actions like registration and expiration, status codes with fixed meanings, and a redacted section that says in the answer itself which parts are withheld and why. What the registry withholds, it now says openly — that is more informative than an empty field.
2. First the map: IANA points to the registry
The internet knows a thousand registries and no central address book of which registry belongs to which domain — except the bootstrap files of IANA: dns.json for the TLDs, ipv4.json and ipv6.json for address ranges. In those stands, per extension or network block, which service must be queried.
That map is what our tool reads before anything is asked: your domain never becomes the host the tool is told to reach, the question is built from the base URL IANA names for your TLD. The registry then sees exactly one thing: the domain you want looked up. The rest stays between you and our server.
3. What the registration answer holds
A domain answer has four lines worth reading. The registrar: who you actually deal with for changes. The status codes: active is normal, clientHold or serverHold take the domain out of DNS, pendingDelete says the deletion phase is running — that is the moment when a domain truly becomes available to someone else. The events: registration date, last change and the expiry date that many people only discover when it is too late. And secureDNS: whether the domain carries DNSSEC.
Mind the difference with DNS itself: RDAP says what stands registered, the DNS lookup says what points the way now, and the DNSSEC reader reads the keys and signatures over the wire. The expiry warning within thirty days stands in the RDAP tool as a warning — because that is the moment when you can still set something right.
4. The other direction: addresses and your own address
RDAP knows the reverse side too: every public IP address belongs to a network block registered at a regional registry — RIPE for Europe, AfriNIC for Africa, APNIC for Asia, ARIN for North America. There the answer speaks not about a person but about a network: name, range, country and the organization in whose name the block stands. That is how you read where a server's provider lives.
You can ask that question about yourself too: Who am I? asks without a target — our server reads your public address from the connection and consults the registry belonging to that address. What comes back is the network within which you enter the internet: the range around your address, the country, and the organization in whose name that block stands. You see exactly that one answer, and no one else sees it.