Check an IP or domain against reputable DNS blacklists — with honest three-state results. A check that fails is reported as unknown, never as clean.
IPv4, IPv6 and domains supported. Domains are checked via the IPs they resolve to.
How this check works — and its limits
Queries DNS blacklists that were individually verified to be alive, to answer over public DNS, and to have unambiguous listing semantics.
Every list gets three possible outcomes: listed, not listed, or couldn't check (timeout, DNS error, or refused query). A failed check is never shown as clean.
When a listing is found, the list itself is sanity-checked (a list that claims the reserved address 127.0.0.1 is listed is treated as broken and its result discarded — per RFC 6471, that's a classic sign of a dead list "listing the world").
Return codes are interpreted per list — e.g. a HostKarma "whitelisted" code is good news, a Tor-exit hit is informational, backscatter means a misconfigured mail server rather than malice.
Not listed ≠ guaranteed clean. Listings change constantly, and the biggest lists can't be queried here at all (see below). Re-check before acting.
Lists checked
Deliberately excluded
Spamhaus ZEN / DBL / CBL — block queries from public DNS resolvers. Check directly: check.spamhaus.org
SURBL, URIBL — refuse queries via public DNS (they return a block sentinel). URIBL lookup · SURBL analysis
SORBS, SpamRats, UCEPROTECT L2/L3, abuse.ch lists — dead, discontinued, or network-level by design (high false-positive rate).