What Is Reverse DNS (PTR Records)?
Normal (forward) DNS maps a name to an IP. Reverse DNS does the opposite — IP to name — using PTR records.
How It Works
IPv4 reverse lookups use the in-addr.arpa domain, with the IP reversed:
8.8.8.8 → 8.8.8.8.in-addr.arpa → dns.google
Enter an IP into the DNS Lookup tool to see its PTR result. The home page also shows the reverse host name for your own IP.
Why It Matters
- Mail servers: whether the sending IP's reverse matches its forward record (FCrDNS) feeds spam scoring. Missing reverse DNS can hurt deliverability.
- Log analysis: helps characterize who is connecting.
Reverse DNS is usually configured by the ISP or data center that owns the IP block, not by the end user.