What is reverse DNS?
Reverse DNS (rDNS) is a DNS lookup that converts an IP address into a hostname. This is stored in a PTR record. Not every IP has a PTR record configured.
What is a PTR record?
A PTR record is the reverse of an A/AAAA record. Instead of domain → IP, it maps IP → hostname. PTR records are commonly used for mail server validation, logging, and network troubleshooting.
Why does reverse DNS sometimes return nothing?
Many consumer IP addresses have no PTR record set, or they return a generic hostname from the ISP. If you are checking a server IP, you may need to configure rDNS at your hosting provider.
How is this different from DNS lookup?
DNS lookup checks records for a domain (A, MX, TXT, NS…). Reverse DNS checks the PTR record for an IP.