Reverse IP Lookup
The hostname an address publishes, and whether that name resolves back to it.
What this tool does, and what it does not
It returns the PTR record: the single hostname the owner of an address has published for it. It then resolves that hostname forward and reports whether it points back at the address you started with.
It does not list every website hosted on an address, and it is worth being clear about why. DNS has no record that maps an address to the names pointing at it; the mapping only runs in one direction. Services offering that list have crawled the web and built a database of names and the addresses they resolved to at the time. That is a useful product, and it is a search of somebody's index rather than a lookup, so its answers are as current as its last crawl. This page does the lookup part honestly instead of implying it can do the other.
Forward confirmation is the point
Anyone who controls an address block can set its reverse record to any name they like, including one they have nothing to do with. A PTR on its own is therefore a claim, not evidence.
Resolving the claimed name forward and finding the original address among the results is what makes it credible, because that half is controlled by whoever owns the domain. Only when both sides agree does the pair mean anything, and that is exactly the check mail servers and log analysis tools apply. It is usually written as forward-confirmed reverse DNS.
Why an address might have no reverse record
Because reverse DNS is delegated with the address block, not with the domain. Whoever owns the block controls it, which means a hosting customer often cannot set their own and has to ask the provider. Residential connections usually carry a generic name assigned by the ISP, or nothing at all, and that is normal rather than a fault.
Where it matters
| Situation | Why the record matters |
|---|---|
| Sending email from your own server | Many receivers reject or penalise mail from an address with no reverse record. Forward-confirmed reverse DNS is close to a baseline requirement. |
| Reading server logs | The hostname often identifies what a visitor is far better than the location does. Names containing ec2, googlebot or a datacentre code tell you immediately. |
| Verifying a crawler | The published way to check a bot is genuine: look up the address, confirm the name belongs to the operator, then resolve it forward. Faking the user agent is trivial; faking both directions of DNS is not. |
How to use it
Enter an IPv4 or IPv6 address and press Look up. The result shows the hostname, the addresses that name resolves to, and whether the pair is forward-confirmed. For location and network details on the same address, use the IP Lookup.
Questions
Does this list every website on an IP address?
No, and no tool can do it from DNS alone. There is no record that maps an address to the names pointing at it; the mapping only runs the other way. Services that offer that list have crawled the web and built a database, which is a different thing from a lookup. What this returns is the PTR record, which is the one name the address owner has published.
What does forward-confirmed mean?
That the hostname the address claims resolves back to that same address. Anyone controlling an address can set its PTR to any name at all, so the reverse record alone proves nothing. Resolving the name forward and finding the original address is what turns a claim into evidence, and it is the check mail servers apply.
Why does an address have no reverse record?
Because nobody set one. Reverse DNS is controlled by whoever owns the address block rather than by whoever uses it, so a customer of a hosting provider often cannot set it themselves and has to ask. Residential connections frequently have a generic name or none at all.
Does reverse DNS matter for sending email?
Yes, more than almost anything else at the connection level. Many receiving servers reject or heavily penalise mail from an address with no reverse record, and forward-confirmed reverse DNS is close to a baseline requirement for a server that sends its own mail.
Is my lookup sent to a third party?
No. The query is made by this server using its own resolver rather than being passed to a commercial lookup API, so the address you check is not shared with anyone else.
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