Reverse IP Lookup

Find the hostname behind an IP address, plus ISP, ASN and location

100% free. This tool needs our server to do the work, so what you submit is sent there, processed and then discarded - it is never stored.

Leave it blank to look up the address you are connecting from. Reverse DNS is published by whoever owns the IP block, so plenty of addresses have no PTR record at all - that is normal, not an error.

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About this tool

Find the hostname published for an IP address. A reverse lookup asks DNS for the PTR record, which is the name the owner of the address block has attached to it - and it is the record mail servers, firewalls and abuse desks check when deciding whether to trust traffic. Leave the field blank to look up the address you are connecting from. Not every address has a PTR record, and that is normal for home connections; for a mail server it is a problem worth fixing.

Workflow

Fix email that is not being delivered

Confirm the server answers and your credentials work before blaming DNS.

  1. 1Test the SMTP serverConnectivity, TLS, certificate and AUTH.Open
  2. 2Check reverse DNSA missing PTR record is a common cause.You are here
  3. 3Inspect DNS recordsVerify SPF and MX are published.Open

How to use this tool

  1. Enter an IP addressType any public IPv4 or IPv6 address, or leave it blank to look up your own.
  2. Run the lookupThe PTR record is queried live from DNS and shown with its TTL.
  3. Check it matchesFor a mail server, the hostname should also resolve forward to the same address.

Key features

  • Shows the actual PTR record with its TTL rather than a cached guess.
  • One click looks up the address you are connecting from, with nothing to type.
  • Explains what a missing record means instead of showing an empty result.
  • Copy button for pasting a hostname straight into a ticket or config.
  • Works for both IPv4 and IPv6 addresses.
  • Free, instant and no signup.

Common uses

  • Checking that a mail server has matching forward and reverse DNS before chasing deliverability.
  • Identifying who owns an address that appears in your server logs.
  • Confirming that a hosting provider set up reverse DNS after you requested it.
  • Investigating an unfamiliar IP in a firewall or abuse report.
  • Finding the hostname behind an address flagged by a monitoring alert.
  • Verifying that a crawler claiming to be a search engine really resolves to one.

Tips for better results

  • For mail servers, the PTR should match the hostname used in the SMTP greeting.
  • A missing PTR on a home or mobile connection is completely normal.
  • Reverse DNS is set by whoever owns the address block, so ask your host to change it.
  • Confirm the forward record too - a PTR that does not resolve back is treated as suspicious.
  • TTL tells you how long a change will take to propagate.
  • Use this together with a ping test when investigating an unfamiliar address.

Mistakes to avoid

  • Expecting every IP to have a hostname - most do not, and that is not an error.
  • Assuming the PTR proves ownership; anyone controlling the block can publish any name.
  • Trusting a crawler because its PTR says Google without checking the forward record too.
  • Trying to look up a private address such as 192.168.x.x, which has no public reverse DNS.
  • Changing reverse DNS at your registrar - it is set by the address block owner, not the domain registrar.

Frequently asked questions

It asks DNS for the PTR record attached to an IP address, which maps the address back to a hostname. It is the opposite direction from a normal lookup, which turns a hostname into an address.

Because the owner of the address block has not published a PTR record for it. That is completely normal for home broadband and mobile connections. For a server that sends email it is worth asking your hosting provider to add one.

Yes. Many receiving mail servers check that a sending address has a PTR record and that the hostname resolves back to the same address. A missing or mismatched record is a common reason mail lands in spam or is rejected outright.

Yes - leave the field blank or press Use my IP, and the lookup runs against the address you are connecting from.

No. That is a different service built from a crawled database. This tool returns the PTR record that DNS actually publishes, which is usually a single hostname for the server itself.

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