Forward-Confirmed Reverse DNS Check
An address passes when its PTR name resolves back to the same address. Enter an IP to check it.
- Free
- No Sign-Up
- Live Lookup
Examples:
Reverse DNS Lookup
How FCrDNS works
Step 1IP → PTR name
Step 2PTR name → A/AAAA addresses
PassThe original IP is among them
Used ByMail servers, SSH UseDNS, some firewalls
Anyone who controls an IP block can set its PTR to any name, including yours. Checking the name forward again proves the name's owner agrees, which is why mail filters rely on it.
Reverse DNS Guides
Questions
What does FCrDNS stand for?
Forward-confirmed reverse DNS, also called full-circle reverse DNS.
Free Tools
More tools
Reverse DNS LookupPTR record for an IP, and whether it is forward-confirmed.DNS LookupA, AAAA, MX, NS, TXT, CNAME, SOA and CAA records for any domain.SPF CheckerValidate an SPF record and count its DNS lookups against the limit of 10.IP Reputation CheckerCheck an IP against spam blocklists and threat feeds at once.
Stop abuse leaving your servers
Frabs watches every VM's outbound traffic and stops spam, scans and floods before the abuse report arrives.