Find the hostname associated with an IP address — a PTR record (reverse DNS) lookup.
Every other tool on this site runs entirely as JavaScript in your browser and never contacts a server at all. This one is a deliberate exception, by necessity: the IP address you enter is sent to this site’s server to run the reverse DNS query — unavoidable, since browsers can’t query DNS directly — using this server’s own DNS resolution, with no third-party service involved. Nothing about the request is logged, stored, written to a cookie, or shared with any third party — it's handled and discarded the moment the response is sent back to you.
This describes only what this specific tool does with what you type into it. It doesn't cover the rest of this site — see the Privacy Policy for how analytics and advertising cookies are handled elsewhere.
A reverse DNS lookup answers the opposite question from a normal DNS lookup: instead of "what IP does this domain point to," it asks "what hostname is registered for this IP address," by querying the IP's PTR record.
This is commonly used to identify a mail server (many mail systems check for a matching reverse DNS record as a basic spam/legitimacy signal), to investigate log entries or an unfamiliar IP from a server's access logs, or just to see what an IP address claims to be.
Not every IP address has a PTR record set up — plenty of legitimate servers and most home internet connections don't have one configured, so no result doesn't necessarily mean anything suspicious.
PTR records require the IP’s owner to explicitly configure them, and many don’t bother — most home/residential IPs and plenty of servers have no PTR record at all. It’s common, not a red flag by itself.
A mismatched or missing reverse DNS record is one of many signals spam filters use — legitimate mail servers typically have a PTR record that resolves back to a hostname matching their forward DNS setup.
No — WHOIS shows domain/IP block registration and ownership details. Reverse DNS just shows what hostname (if any) is configured to answer for that specific IP address.
Yes — "PTR lookup" and "reverse DNS lookup" describe the same thing; PTR is the technical name of the DNS record type this tool queries.