A WHOIS and RDAP API that gives you a straight answer
One GET request, one JSON response: registered or free, expiry date, registrar, nameservers. RDAP when the registry offers it, WHOIS port 43 when it does not.
One request, one answer
Works without a key too, at anonymous rate limits.
curl https://api.domain-sentinel.com/v1/lookup/example.com \
-H "Authorization: Bearer ds_live_your_key"{
"domain": "example.com",
"available": false,
"checkMethod": "rdap",
"statuses": ["client transfer prohibited"],
"nameservers": ["a.iana-servers.net", "b.iana-servers.net"],
"events": [
{ "eventAction": "expiration", "eventDate": "2026-08-13" }
]
}What you get
RDAP first, with fallbacks that make sense
We query the registry's RDAP server, fall back to its WHOIS port 43 server, and finish with a DNS delegation check when neither answers.
Honest availability
available is true, false or null. When only DNS could answer, we say maybeAvailable instead of inventing a status.
Clean JSON and an OpenAPI spec
Statuses, events, nameservers and registrar entities in a stable schema you can generate a client from.
About 1200 TLDs
Every extension in the IANA RDAP bootstrap plus a curated WHOIS server list for the holdouts, resynced daily.
Rate limits and pricing
| Access | Limit |
|---|---|
| Anonymous (no key) | 5/min, 50/day |
| Free API key | No enforced limit |
Keyed usage is counted per month. Paid plans with quotas come later; current free keys keep working.
Frequently asked questions
What is the difference between WHOIS and RDAP?
RDAP is the standardized successor to WHOIS: same registry data, but served as structured JSON over HTTPS instead of free-form text on port 43. We use RDAP whenever the registry provides it and parse WHOIS only for TLDs that still lack an RDAP server.
Is the API really free?
Yes. Anonymous requests are limited to 5 per minute and 50 per day. With a free account you create an API key and there is currently no enforced request cap.
Which domains can I look up?
Any domain in the roughly 1200 extensions we support: everything in the IANA RDAP bootstrap plus a curated set of WHOIS servers. The full list is on our supported TLDs page.
How fresh is the data?
Lookups are served from a cache for up to one week. A force refresh performs a live registry query unless the cached answer is under 24 hours old.
Do I need an API key?
No key is needed to try it. For anything beyond a few requests, create a free account and generate a key in the dashboard under API Keys.
Ship your domain feature this afternoon
Free key, JSON in one request, OpenAPI spec to generate your client.
Create your free account