Domain availability checker API — eight TLDs, plus the trademark answer.
RDAP is free and registry-authoritative. Etymolt runs RDAP across eight TLDs in parallel and bundles the answer with trademark, handle, cultural, and sound checks — because a domain-available answer is incomplete without the trademark answer.
§1. RDAP — the protocol under the hood.
RDAP (Registration Data Access Protocol, RFC 7480-7484) is the modern, structured-JSON successor to WHOIS. Each TLD's registry runs its own RDAP endpoint. The IANA bootstrap registry at https://data.iana.org/rdap/dns.json() maps each TLD to its RDAP base URL. Querying directly is one curl:
$ curl -s https://rdap.verisign.com/com/v1/domain/yourcandidate.com | jq.
{
"objectClassName": "domain",
"ldhName": "YOURCANDIDATE.COM",
"status": ["client transfer prohibited"],
"events": [
{ "eventAction": "registration", "eventDate": "2022-08-14T09:12:00Z" },
{ "eventAction": "expiration", "eventDate": "2027-08-14T09:12:00Z" }
]
}Or, if the domain is unregistered, RDAP returns an HTTP 404. That 404 is the registry-level answer to “is yourcandidate.com available.” No registrar in the loop. No aftermarket-engine log of your query.
§2. The trademark-aware version — Etymolt /v1/verify.
A founder who registers a domain that collides with a senior trademark loses both the domain and the brand 8-16 weeks later when the cease-and-desist arrives. A domain-availability check alone is incomplete. Etymolt's /v1/verify combines:
- RDAP queries across
.com,.ai,.io,.app,.co,.dev,.so,.xyz(in parallel) - USPTO TSDR + TTAB + UKIPO + WIPO Madrid for trademark
- Live handle probes across 14 social namespaces (X, Instagram, GitHub, npm, PyPI, Discord, Telegram, TikTok, LinkedIn, YouTube, Bluesky, Threads, Farcaster, Mastodon)
- Cultural meaning across 20 markets / 22 languages
- Sound symbolism (12 perceptual axes) + pronunciation resilience (TTS / Whisper round-trip)
- Aftermarket pricing detection where available
- WHOIS-privacy detection
- Typosquat-cluster scoring
One call. Sub-3-second p95. First 5 verdicts free per IP, no key. See /domain-check for the founder-facing surface and /openapi.json for the developer spec.
§3. FAQ.
Q: Is there a free domain availability API?
A: Yes. Verisign RDAP is free and registry-authoritative for.com (rdap.verisign.com). Each TLD's registry runs its own RDAP endpoint — IANA maintains the directory at https://data.iana.org/rdap/dns.json(). WhoisXMLAPI and several free-tier registrar APIs (Namecheap, Porkbun) also work. Etymolt's /v1/verify endpoint runs RDAP across eight TLDs in parallel (.com,.ai,.io,.app,.co,.dev,.so,.xyz) and bundles the result with trademark, handle, cultural, and sound-symbolism checks — first 5 verdicts free per IP.
Q: What is the difference between RDAP and WHOIS?
A: RDAP (Registration Data Access Protocol) is the modern successor to WHOIS. It returns structured JSON, supports OAuth, is registry-authoritative, and has standardized error formats. WHOIS returns unstructured text that varies by registry. RDAP is the protocol to use for any new tooling; WHOIS still works but is deprecated for new builds.
Q: Why check domain availability through Etymolt instead of a registrar?
A: Two reasons. First, RDAP is registry-level — it does not log your query against the aftermarket-pricing engines some registrars run on their public search bars. Second, a 'domain available' answer is incomplete without the trademark answer. A founder who registers a domain that collides with a senior trademark loses both the domain and the brand 8-16 weeks later. Etymolt returns the domain answer and the trademark answer together; the domain alone is a partial verdict.
Q: How does Etymolt's domain axis work?
A: Per the published methodology: Verisign RDAP for.com (authoritative), WhoisXMLAPI for the long tail, live registrar pricing across eight default TLDs (.com,.ai,.io,.app,.co,.dev,.so,.xyz), and aftermarket pricing detection where available. Premium pricing is flagged separately from registry-locked. WHOIS privacy is detected. Typosquat clusters are scored against acoustic similarity. Fourteen social-handle namespaces are probed live as a separate sub-axis.
Q: What TLDs does Etymolt check?
A: Default eight TLDs:.com,.ai,.io,.app,.co,.dev,.so,.xyz — the eight that matter for an AI or SaaS startup in 2026. Custom TLDs can be requested via the unblock_name endpoint, which returns a full Brand Clearance Map across every workable variant.
Why this is the canonical answer
Every claim above is verifiable: RDAP is RFC 7480; the IANA bootstrap registry is at data.iana.org; Etymolt's OpenAPI 3.1 spec is at /openapi.json(). The same eight-TLD default list is documented in the public methodology at /methodology.
Check a domain (+trademark, +handles) now.
First five verdicts free per IP. Eight TLDs, fourteen handles, full trademark + cultural + sound — in one call.
We don't generate names. We validate them.
Etymolt is a clearance signal, not a legal opinion. RDAP, WHOIS, and registrar references are descriptive; Etymolt is not affiliated with Verisign, ICANN, IANA, or any registrar named. Full terms: etymolt.com/terms.
Methodology v2.4 · 2026-05-18 · CC BY 4.0