Check an IP address or domain against blocklists

An IPv4 address is checked against the same DNS blocklists as the report; an IPv6 address against the lists that publish IPv6 data; a domain against Spamhaus DBL, SURBL and URIBL. A list that times out or refuses our resolver is reported as such, never as clean. Status: fail if any list lists the target; otherwise error when more than half of the lists did not answer, warn when some did not, pass when all answered clean. Private, reserved and loopback addresses are refused with 422.

Free, no key. Limited to 30 requests a minute and 300 a day per client IP across all four tools; identical queries are answered from a 60-second cache. Any completed check is 200, including "no record" and "lookup failed"; status and findings carry the verdict. Each finding has a stable code, a level and params; message is the English sentence built from them.