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Reverse DNS

Find the PTR hostname behind a public IPv4 or IPv6 address: the name its owner set up for reverse DNS.

RECON · SERVER-SIDE · RATE LIMIT 30/MIN

Rate limited: 10 runs in a burst, 30 per minute. Results are never stored. Too long to share as a link.

HISTORY

Your last 5 runs appear here for 7 days, on this device only.

RESULT

Fill in the form and run the tool; the result appears here.

Reverse DNS looks up the PTR record for an IPv4 or IPv6 address and returns every hostname that address resolves back to, the opposite direction of a normal DNS Lookup.

How to read the result

The result lists each PTR name found for the address. An empty list means no PTR record is configured, which is normal for most consumer and cloud addresses but unusual for a production mail server.

When the reverse name also resolves forward back to the same address (forward-confirmed reverse DNS, or FCrDNS), the address and hostname are consistent with each other, which many mail filters check before accepting a message. This tool does not run that forward check for you: look the PTR name up in DNS Lookup to confirm it. Private and reserved addresses are refused.

Defender tips

  • Set a PTR record for anything that sends mail. Most receiving mail servers weight missing or mismatched reverse DNS heavily in their spam score.
  • Do not put internal hostnames in a PTR record for a public IP; it hands an attacker naming conventions for free.
  • Verify PTR ownership after an IP reassignment (new server, moved cloud instance): a stale PTR record still describing the previous tenant is a common lingering trace.

FAQ

Why is the PTR record empty?

No reverse zone has been delegated for that address, or no record was added to it. It does not mean the address is unreachable, only that reverse lookups return nothing.

Can one address have more than one PTR name?

Yes. Multiple PTR records are valid, though most mail and security tooling only reads the first one returned.

What is FCrDNS and why does it matter?

Forward-confirmed reverse DNS is when the PTR name's own forward lookup points back to the original address. It is a cheap consistency check many spam filters and some access controls rely on.