Enter an IP address to find its PTR (reverse DNS) hostname(s).
A reverse DNS lookup runs a normal DNS query backwards: instead of asking "what IP does this name point to", it asks "what name claims this IP". The answer comes from a PTR record, published by whoever controls the IP address — usually the hosting provider or ISP, not the website owner.
Enter an IPv4 or IPv6 address above to see its PTR record, if it has one.
A PTR record is a claim made by the owner of an IP block. Because only the address holder can publish it, it is harder to fake than a forward DNS record — which is exactly why mail servers lean on it.
What it does not tell you is who owns the website at that address. A shared hosting server running a thousand sites has one PTR record, usually something generic from the host. To find the owner of an address range, use a WHOIS lookup instead.
If you run a mail server, reverse DNS is close to mandatory. Receiving servers commonly check that the sending IP has a PTR record at all, and many go further and require forward-confirmed reverse DNS: the PTR must resolve to a hostname, and that hostname must resolve back to the same IP.
A sending IP with no PTR record, or one still carrying the generic name the hosting provider assigned, is a well-known spam signal. It is one of the cheapest deliverability problems to fix and one of the most frequently overlooked — the fix is a support request to whoever controls the IP, since you cannot set it in your own DNS zone.
An empty result is common and not necessarily a fault. Residential and mobile IP ranges often have generic PTR records or none at all, and plenty of cloud instances ship without one until someone configures it.
Reverse DNS for IPv4 lives under the in-addr.arpa zone, and IPv6 under ip6.arpa. Delegation of those zones follows the address allocation, so if an address sits inside a block that was never properly delegated, no PTR record can exist regardless of what the end user does.
It is a query that takes an IP address and returns the hostname published for it in a PTR record. It answers "what name does this address claim" rather than "what address does this name use".
Because whoever controls the address block has not published a PTR record for it. This is normal for residential and mobile connections, and common for new cloud servers. Only the address holder can add one, so it is a request you make to your ISP or hosting provider.
Not from your own domain's DNS zone. Reverse DNS is delegated with the IP address range, so it has to be set by the organisation that holds the range — your hosting provider, cloud platform or ISP. Most offer it as a setting in their control panel.
Yes. Many receiving mail servers check that a sending IP has a valid PTR record, and some require that the hostname resolves back to the same address. Missing or generic reverse DNS makes your mail significantly more likely to be rejected or filtered.