Domain Search

Domain Search checks whether a domain name is registered, across up to 68 top-level domains in one go. Type a name, pick a TLD list, and every combination is looked up against the registry that holds the record, not a reseller database or a cached index. The answer for each domain is one of three things: available, taken, or unknown.

Every lookup asks RDAP first. RDAP is the Registration Data Access Protocol (RFC 9083), the structured JSON successor to WHOIS, and it is authoritative: a 404 from a registry RDAP server means the name genuinely is not registered. The list of which server serves which TLD comes from the IANA bootstrap file published under RFC 9224. For the several hundred TLDs that still have no RDAP service, most country-code zones among them, the lookup falls back to WHOIS on TCP port 43, using a per-registry table of servers and of the exact phrase each one uses to say "no such domain". When a bundled WHOIS host has gone stale, IANA is asked which server serves that TLD today.

The third verdict is the one that makes the other two trustworthy. WHOIS is unstructured text, and a registry that is rate-limiting you, refusing your query, or answering about a different name will happily produce a response that a naive substring match reads as "free". Those cases are reported as unknown with the reason attached rather than being guessed at, because "available" is the answer people act on. Availability services that answer "Available" or "Not Available" are read with negation awareness, records that describe a parent zone are rejected, and registries that echo your query back before saying nothing was found are handled explicitly.

Because registry lookups need a raw TCP socket and cross-origin HTTPS requests, this tool runs on our server rather than in your browser, the exception to how most Toolz tools work. The names you check are sent to Toolz to perform the lookups and are not stored. Results stream back as they arrive, so the fast registries answer while the slow ones are still thinking, and any name that comes back available is shown with the registry that operates the TLD and links to register it.

A short example shows how the bulk domain availability checker counts its work. Type acmecloud, acme-cloud in the name field and click the Startup preset, which selects ten extensions: com, net, org, io, co, ai, app, dev, xyz and me. The counter beside the form reads 20 lookups before you search, two names times ten extensions, and a repeated name is dropped rather than counted twice. Switch to Popular and the same two names cost 76 lookups against 38 extensions. Forty names or 240 lookups is the ceiling for one search, so a longer shortlist goes in batches.