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