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Reverse DNS Lookup

Find the PTR record (the reverse DNS hostname) of any IPv4 or IPv6 address, and check that the hostname resolves back to the same IP, the test mail servers apply.

Look up reverse DNS

Enter an IPv4 or IPv6 address to find its PTR hostname and check that the hostname points back. Free, no signup.

What reverse DNS is

Normal DNS turns a name into an address. Reverse DNS goes the other way: it turns an IP address into a hostname, using a PTR record. The PTR lives under a special name built from the address written backwards. For 192.0.2.10 that is 10.2.0.192.in-addr.arpa; for an IPv6 address it is all 32 hexadecimal digits, reversed and separated by dots, under ip6.arpa. This tool builds that name for you, reads the PTR record, and then looks the returned hostname up again to see whether it points back to the address you started with.

Who controls a PTR record

Reverse zones belong to whoever holds the IP block, not to whoever holds the domain. That is why the DNS panel with your A and MX records has no place to set one. For a cloud server or VPS, the PTR is set in the provider's console, often in a field called reverse DNS. For a dedicated server or a business internet line, ask the hosting company or ISP that assigned the address. If you send mail through Microsoft 365, Google Workspace or another hosted service, their IP addresses carry their own PTR records and there is nothing for you to set.

Forward confirmation and why mail servers care

A PTR record on its own proves little, because anyone who controls a reverse zone can publish any name in it. Mail receivers therefore check both directions: the IP must have a PTR, and the hostname in it must resolve back to the same IP. This is forward-confirmed reverse DNS (FCrDNS). A sending IP that fails it looks like a home connection or a compromised machine, and many receivers reject or penalise its mail before they look at SPF, DKIM or DMARC. To run this test for every IP behind a domain's MX records at once, use the FCrDNS checker.

How to read the result

The result shows the reverse name that was queried, each PTR hostname, the addresses that hostname resolves to, and the verdict. Forward-confirmed means the hostname resolves back to your IP. Points elsewhere means it resolves, but to other addresses. No address means the hostname has no A or AAAA record for that IP version. An IP with several PTR records is legal but unhelpful: receivers often check only the first. A hostname that contains the IP or words like dynamic or pool looks like a provider default, which some filters score as residential.

Common problems and fixes

A new VPS often has no PTR, or a generic one such as static.10.2.0.192.provider.net; set it to a name in your own domain, like mail.example.com, and give that name an A record pointing at the IP. A PTR that is set but has no matching A record fails forward confirmation; add the A record. A server with an IPv6 address is regularly missing its IPv6 PTR, and receivers that connect over IPv6 then see no reverse DNS at all. Private addresses such as 10.0.0.0/8 or 192.168.0.0/16 have no reverse records in public DNS.

What This Checks

  • PTR record of an IPv4 or IPv6 address
  • The in-addr.arpa or ip6.arpa name that was queried
  • Forward confirmation: does the PTR hostname resolve back to the IP
  • Several PTR records, or a generic provider hostname
  • Private and reserved addresses that have no public reverse DNS

Common Fix Path

  • Set the PTR with whoever assigned the IP address
  • Point the PTR at a hostname in your own domain
  • Give that hostname an A or AAAA record for the same IP
  • Set reverse DNS for IPv6 addresses as well as IPv4

Frequently Asked Questions

How do I do a reverse DNS lookup?
Enter an IPv4 or IPv6 address above. The tool queries the PTR record under in-addr.arpa or ip6.arpa and then resolves the hostname it finds to check that it points back to the same IP. On the command line, dig -x 192.0.2.10 or nslookup 192.0.2.10 does the first half of that.
Why does my IP address have no PTR record?
Because nobody set one in the reverse zone, which belongs to whoever assigned the IP: your hosting, cloud or internet provider. New servers often start without a PTR or with a generic one. Set it in the provider's console or ask the provider to set it.
How do I set a PTR record?
In the control panel of whoever owns the IP address, usually under reverse DNS, or by asking that provider. Choose a hostname in your own domain, such as mail.example.com, and make sure that hostname has an A or AAAA record pointing at the same IP, so the PTR forward-confirms.
What is forward-confirmed reverse DNS (FCrDNS)?
It means the PTR hostname of an IP resolves back to that same IP. Mail receivers use it as a basic trust check on sending servers. This page tests one IP; the FCrDNS checker tests every IP behind a domain's MX records.
Can one IP address have more than one PTR record?
Yes, DNS allows it, but it is a poor idea for mail servers. Many receivers look only at the first PTR they get, and the order is not fixed, so the check can pass one time and fail the next. Use one PTR per address.
Does reverse DNS matter for a website?
Hardly. Browsers never check it. It matters for sending email, where receivers test it, and it shows up in server logs, traceroutes and some SSH and access-control setups that resolve client addresses.

Machine-Readable Evidence

AI assistants and automation can cite the stable explanation page, then fetch the live check result for a specific domain.

GET https://intodns.ai/api/dns/lookup?domain=8.8.8.8.in-addr.arpa&type=PTR

Related Tools and Citations

FCrDNS Checker (all mail-server IPs)SMTP TLS CheckerBlacklist CheckerA and AAAA Record LookupRun the full domain scan