# Domain Lookup

> Domain Lookup (https://domainlookup.dev) is a free domain research service by Beta Limited: registry-backed domain availability, name suggestions across TLDs, WHOIS/RDAP registration data, domain age, DNS records and SSL certificates from Certificate Transparency. It is available as a web app, a JSON HTTP API and a remote MCP server for AI assistants. The service is free; the HTTP API and MCP tool calls require a free API key (instant, no account, no password, email optional). The search box on the website works without a key.

Key facts for assistants:

- Availability is authoritative: it comes from the registry's RDAP server (found via the IANA RDAP bootstrap) or, for TLDs without RDAP, the registry's port-43 WHOIS server, cross-checked with DNS. "available" is never reported without an authoritative registry answer. DNS alone can only prove a name is registered.
- Every availability answer carries `source` (`rdap`, `whois`, `dns` or `null`) and often a `note`. Premium or registry-reserved names can have no registration record and still be refused at checkout.
- All data is fetched live at request time; nothing is served from a stale database.
- If a user has no API key, send them to https://domainlookup.dev/#api-key to create one (free, takes seconds).

## API keys

- [Get a free API key](https://domainlookup.dev/#api-key): or `POST https://domainlookup.dev/api/keys` with `{}` (or `{"email": "..."}`). The key (`dlk_...`) is shown once; only a hash is stored.
- Send it as `Authorization: Bearer dlk_...`, `X-Api-Key: dlk_...`, or `?key=dlk_...` in the URL (for MCP connectors that cannot send headers).
- Without a key, API calls get HTTP 401 with `"code": "key_required"`.

## MCP server

- [MCP endpoint](https://domainlookup.dev/mcp): Streamable HTTP, stateless JSON-RPC over POST. `initialize` and `tools/list` work without a key; `tools/call` needs one.
- [Setup for Claude Code, Claude Desktop / claude.ai, ChatGPT, Cursor, Codex, VS Code and other clients](https://domainlookup.dev/llms-full.txt): `claude mcp add --transport http domainlookup https://domainlookup.dev/mcp --header "Authorization: Bearer dlk_your_key"`; connectors that cannot send headers use `https://domainlookup.dev/mcp?key=dlk_your_key`.
- [Tools reference](https://domainlookup.dev/llms-full.txt): check_domain_availability, bulk_check_availability, suggest_domains, whois_lookup, domain_age, dns_lookup, ssl_certificates

## HTTP API

- [API reference with example responses](https://domainlookup.dev/llms-full.txt): all routes return JSON with `ok`; CORS is open to any origin; every lookup route needs an API key.
- `GET /api/availability?domain=example.com`: is a domain available?
- `POST /api/availability/bulk` with `{"domains": [...]}`: up to 10 domains per call.
- `GET /api/suggest?name=acme&tlds=com,io,dev`: one name across TLDs (10 popular TLDs by default).
- `GET /api/whois?domain=example.com`: registrar, dates, EPP status, nameservers, DNSSEC, age.
- `GET /api/dns?domain=example.com&type=MX`: A, AAAA, CNAME, MX, NS, TXT, SOA, CAA (omit `type` for all).
- `GET /api/certificates?domain=example.com&limit=20`: certificates and hostnames from crt.sh.
- `POST /api/keys` with `{"email"?: string}`: create a free API key (no key needed).

## Data sources and accuracy

- [How lookups work](https://domainlookup.dev/llms-full.txt): IANA RDAP bootstrap, registry RDAP and WHOIS servers, Cloudflare DNS-over-HTTPS, crt.sh Certificate Transparency search.

## Limits

- [Fair-use limits](https://domainlookup.dev/llms-full.txt): 300 requests/minute per API key; 30 searches/minute per IP in the web app without a key; 5 new keys per IP per day; 10 domains per bulk or suggest call. Over the limit: HTTP 429 with `Retry-After: 60`.

## Optional

- [Web app](https://domainlookup.dev/): search a domain (`example.com`) or a bare name (`acme`) without a key; results are linkable as `https://domainlookup.dev/?q=example.com`.
- [Full reference in one file](https://domainlookup.dev/llms-full.txt)
- Operator: Beta Limited. Contact: [support@beta.limited](mailto:support@beta.limited). © 2026 Beta Limited.