This tool performs a Reverse DNS lookup: given an IP address it finds the associated hostname (PTR record). Both IPv4 and IPv6 are supported. Forward Confirmed rDNS (FCrDNS) is also verified.
A PTR (pointer) record lives in the reverse DNS zone and maps an IP address to a hostname. Unlike an A record (domain â IP), PTR works in the opposite direction: IP â domain. Reverse zones are .in-addr.arpa for IPv4 and .ip6.arpa for IPv6.
Forward Confirmed rDNS (FCrDNS) is an extra check: reverse DNS (IP â name) and forward DNS (name â IP) must return matching results. Mail servers and anti-spam systems use FCrDNS; messages from IPs with a mismatched PTR are frequently blocked or sent to spam.
Enter your IP address (IPv4 or IPv6) in the field on the tool page and click "Check". The system will perform a reverse DNS lookup and show the domain associated with that address, as well as the result of the Forward Confirmed rDNS check.
This means that no reverse DNS record is configured for the specified IP address. This often happens with dynamic IPs or addresses allocated by a provider without rDNS. To add a PTR record, contact your hosting provider or network administrator.
FCrDNS confirms that the PTR record of the IP matches the actual domain. First, the domain is found by IP (reverse lookup), then this domain is resolved to an IP (forward lookup). If the IPs match, the record is considered confirmed, which is critical for mail servers and anti-spam filters.