Reverse DNS Lookup

Reverse DNS (PTR) lookup

Which hostname does this IP address claim, and does that name point back?

Try: 8.8.8.8

How this lookup works

Reverse DNS turns an IP address back into a host name. For IPv4, the address's octets are reversed under in-addr.arpa: 203.0.113.25 becomes 25.113.0.203.in-addr.arpa. For IPv6, the full 32-digit address is written out nibble by nibble, reversed, under ip6.arpa. The check queries that name for a PTR record through a public resolver.

It then looks up the A or AAAA records of each returned name to see whether they point back to the original address. When they do, the address has forward-confirmed reverse DNS (FCrDNS).

How to read the results

  • PTR and forward match: the address has FCrDNS. Mail receivers, including Gmail, require this for sending IPs.
  • PTR, but the name doesn't resolve back: many receivers treat this like having no PTR at all. Add an A or AAAA record for the name, or change the PTR.
  • No PTR record: whoever controls the address block hasn't published one. That's normal for most client addresses and a problem for mail servers.
  • Generic-looking names such as 203-0-113-25.dynamic.example-isp.net signal a residential or dynamic address. Spam filters penalise mail from them.

Who can change it

PTR records live in the zone of whoever holds the IP block, which is usually your ISP or cloud provider, not your own DNS provider. Most cloud platforms let you set it on the IP resource; ISPs set it on request for static business addresses. The reverse DNS guide lists where to change it on common platforms.

Updated 26 October 2026

Related checks

  • What Is My IP?

    Which public address does the internet see for me, and what does its reverse DNS say?

  • IP Whois

    Who owns this IP address, and where do I report abuse from it?

  • BGP Route Lookup

    Which network announces this address block, and who is responsible for it?

FAQ

Why is no hostname returned?

Not all IP addresses have reverse DNS configured. The owner of the IP block must set up a PTR record pointing back to a hostname. Many cloud and hosting providers don't configure PTR records by default.

What is forward-confirmed reverse DNS?

The PTR record for an IP gives a hostname; FCrDNS means that hostname has an A or AAAA record pointing back to the same IP. Both halves must agree before receivers trust the name.

Why doesn't the hostname match my domain?

Reverse DNS is managed by the organization that owns the IP address block, not the domain owner. Your hosting provider controls the PTR record and may set it to their own hostname.