Reverse DNS (PTR) lookup

A reverse DNS lookup turns an IP address back into the hostname its owner has assigned to it (the PTR record).

How to use the reverse dns (ptr) lookup

  1. Enter an IP address.
  2. Press Look up.
  3. Read the PTR hostname the IP's owner has assigned, if any.

What reverse DNS tells you

Normal DNS turns a hostname into an IP; reverse DNS does the opposite, looking up the PTR record the IP's owner has set. Mail servers use it to gauge whether a sender is legitimate. Many residential and some hosting IPs have no PTR configured — that's normal, not an error. To go the other direction, use the DNS lookup tool.

Code & API examples

Use this from the command line or your code. The API is free, GET-only, and returns JSON.

API (curl)
curl "https://vpn.golf/api/tools/reverse-dns?ip=8.8.8.8"
Shell (dig)
dig -x 8.8.8.8 +short

See all endpoints at /api/tools/.

Frequently asked questions

Normal DNS turns a hostname into an IP. Reverse DNS does the opposite — it looks up the PTR record an IP's owner has set, often used by mail servers to check legitimacy.

PTR records are optional and set by whoever controls the IP block. Many residential and some hosting IPs simply don't have one configured.

A PTR (pointer) record is the DNS entry that maps an IP address back to a hostname. It lives in a special reverse zone (in-addr.arpa for IPv4) maintained by the IP block's owner.

Only whoever controls the IP block — usually the ISP or hosting provider. Customers often must request a PTR change through their provider rather than setting it themselves.

Receiving mail servers check whether a sending IP has a PTR that matches its forward DNS. A missing or mismatched PTR is a common reason legitimate mail gets flagged as spam or rejected.

It's when an IP's PTR hostname also resolves forward back to that same IP. This round-trip match (FCrDNS) is what mail servers and security tools use to trust that a hostname is genuine.

PTR records reflect the infrastructure's naming, not the sites hosted on it. One server can host many domains, so its PTR is usually the provider's generic hostname, not any individual website.

Technically yes, but it's discouraged and many tools only read the first. Best practice is a single PTR per IP that matches the host's forward record.

A regular (forward) lookup answers 'what IP is this hostname?'; reverse answers 'what hostname is this IP?'. They use separate records, and one can exist without the other.

Yes. IPv6 uses PTR records in the ip6.arpa reverse zone. They're less commonly configured than IPv4 PTRs because the address space is so large, but the lookup works the same way.

Most likely no PTR record exists for that IP, which is common for residential and many cloud addresses. It can also mean the reverse zone isn't delegated to a working nameserver.

No. The query goes to public DNS infrastructure, not to the target IP, and vpn.golf keeps no logs of what you look up. The result is only the PTR the IP's owner chose to publish.
Related tools
IP address lookup DNS lookup tool WHOIS lookup
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