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Domain Availability Checker

domain-availability-checker.underscoredone.com · x402

Give this API up to 10 domain names and it tells you whether each has a registration record at the official registry. It uses RDAP, the structured replacement for WHOIS, so there is no free-text parsing. Each domain comes back as 'registered', 'unregistered', or 'indeterminate' when the registry has no RDAP for that ending. 'Unregistered' means no record was found, which usually means available - but reserved and premium names also return no record. Registration status only; no pricing.
Name and description as published by x402 Bazaar

Live

Last successful check: 25 Oct 2026, 18:33 UTC.

answered, last 24 hours
100%
answered, last 30 days
100%
How addrbook checks →

Connect

https://domain-availability-checker.underscoredone.com/check

x402: an unpaid request gets a 402 with the price and pay-to wallet. addrbook never pays.

Who's behind it

Listed by
  • x402 Bazaarlast seen UTC
Wallets named
  • 0xe9740820225b3918b4ddd1292c7ca4ca0e2c2f08named by x402 Bazaar
Listed since

Checks by endpoint

HostProtocolStateLast checked (UTC)Last answered (UTC)24 hours30 daysTools
domain-availability-checker.underscoredone.comx402Live100%100%—

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