Reverse IP lookup
Hostname (PTR), geo-location and ISP for any public IP address.
How this tool works
Reverse DNS lookup (PTR record) returns the hostname mapped to an IP — the inverse of the classic A record. The tool also overlays geo data (country, region, city), ISP and ASN. This lets you identify the provider and hostname behind a request in server logs, and verify whether a mail server has clean FCrDNS (Forward Confirmed Reverse DNS — required by many spam filters).
Typical use cases
- Map suspicious IPs from web logs to a hostname and ISP
- Before blocking an IP, verify it is not Googlebot, BingBot or another legit crawler
- Check FCrDNS for mail servers — the A record must resolve back to the PTR, otherwise mail gets penalized
- Identify the source ASN under suspected DDoS
Frequently asked questions
Why does an IP have no PTR?
The ISP has to set PTR explicitly — for residential lines it is often empty, for server providers (Hetzner, AWS) always populated. Missing PTR makes a mail IP suspect to many filters.
What is FCrDNS and why does it matter?
Forward Confirmed Reverse DNS: the PTR points to a hostname whose A record points back to the same IP. Mail servers without clean FCrDNS often land in spam — Gmail, Outlook and others enforce it.
Does it support IPv6?
Yes — IPv6 addresses are converted to ip6.arpa PTR lookups.
How do I tell real Googlebot from fakes?
Real Googlebot has a PTR on *.google.com or *.googlebot.com, and the A record of that hostname must resolve back to the same IP (FCrDNS). If both match, it is genuine.
Are private IPs supported?
No — 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 and loopback are rejected. They have no public PTR.
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