What is Reverse DNS?
Reverse DNS (rDNS) is the process of resolving an IP address back to a domain name. It's the opposite of a forward DNS lookup (domain → IP). Reverse DNS uses PTR (Pointer) records stored in the .arpa domain.
Common Uses
- Email deliverability: Many mail servers reject emails from IPs without valid rDNS
- Network troubleshooting: Identify which server or service an IP belongs to
- Security analysis: Verify if an IP matches its claimed hostname
- Access logs: Convert IP addresses in server logs to readable hostnames
How It Works
When you enter an IP like 8.8.8.8, the tool reverses the octets (8.8.8.8.in-addr.arpa) and queries for a PTR record. For IPv6, the address is expanded and each nibble is reversed under .ip6.arpa.
Not all IP addresses have PTR records — rDNS must be configured by the IP owner (usually the ISP or hosting provider).