What is a PTR record?
A PTR record maps an IP address to a hostname. It is the reverse-DNS counterpart to an A or AAAA record, which maps a hostname to an IP address.
Relevant standard: RFC 1035 — Domain Names — Implementation and Specification
NETWORK DIAGNOSTICS
Reverse DNS lookup.
Find the PTR hostname assigned to a public IPv4 or IPv6 address and check whether it resolves back to that address.
Only public addresses are accepted. Lookups are limited to 10 per visitor per hour and 10 per IP address per day.
What this reverse DNS lookup checks
A reverse DNS lookup queries the PTR record for an IP address. For IPv4, it reverses the address under in-addr.arpa; for IPv6, it reverses every hexadecimal digit under ip6.arpa. This is the same kind of query made by dig -x.
The result also performs a forward-confirmed reverse DNS check: it resolves each returned PTR hostname for A and AAAA records, then reports whether one of those records matches the submitted address.
Frequently asked questions
Technical context and standardsWhat does forward-confirmed reverse DNS mean?
Forward-confirmed reverse DNS checks that a PTR hostname resolves back to the original IP address through an A or AAAA record. It helps detect an inconsistent reverse-DNS setup, but it is not proof of ownership or trustworthiness.
Why is there no PTR record for an IP address?
Reverse DNS is optional. The organisation controlling an address block may leave it unset, delegate it elsewhere or use it only for selected servers. A missing PTR record does not prevent normal internet connectivity.
Why can the result differ from my own dig command?
DNS answers can vary by resolver, cache state, network location and time. This tool uses the PacketPint server’s configured DNS resolver, so its result may differ from a query made through your own resolver.