Free tool · Reverse DNS
Reverse DNS bulk lookup
Paste up to 50 IP addresses (IPv4 or IPv6, any whitespace or comma-delimited format). We resolve PTR records for each in parallel and return the results in one go. No signup.
Frequently asked questions
What is reverse DNS / PTR?
Forward DNS resolves names to IPs (acme.com → 1.2.3.4). Reverse DNS resolves IPs to names (1.2.3.4 → smtp.acme.com). PTR records live in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zones and are usually controlled by whoever owns the IP allocation, not the domain.
Why does it matter?
Email deliverability: receivers check that the sending IP has a PTR that resolves back to a name in your sending domain. Mismatched or missing PTR is a strong spam signal at major receivers. Network forensics: knowing which name an IP claims to be (or fails to claim) helps confirm whether traffic patterns make sense. Hosting provider inference: PTR often reveals the underlying provider even when the domain is hidden behind a CDN.
Why is the result empty for some IPs?
Many cloud-hosted IPs (especially residential / consumer ISPs and some cloud egress IPs) have no PTR set. That's normal. Empty result means "no PTR" - the IP is reachable but the operator did not configure reverse DNS. Different from "lookup failed" which we surface as an error column.
Can I check IPv6 too?
Yes - paste IPv6 addresses in the same input. We auto-detect family (4 vs 6).
Why is there a 50-IP limit?
Reverse DNS lookups are individual UDP queries to public resolvers. Without a cap, batch sizes balloon and the tool becomes a port-scan-by-other-means. 50 is enough for most casual triage; for larger jobs run dig in a script or use the Wiredepth REST API.