Reverse DNS Lookup
Resolve IP addresses to hostnames and confirm a crawler with the forward-confirmed check the search engines document.
About this tool
Resolves IP addresses to hostnames, and where the hostname belongs to a search engine, performs the verification those engines actually publish.
**A user agent is not evidence.** It is a string any client can send, and plenty of scrapers send Googlebot's. The documented way to confirm one is a **forward-confirmed reverse DNS lookup**: resolve the address to a hostname, check that hostname is on the right domain, then resolve the hostname back and check it returns the address you started with.
**Only the round trip proves anything.** A reverse lookup on its own can be set to say whatever the owner of the address block likes — that is the whole reason the second step exists. Each step is reported separately here, so a partial result reads as partial rather than as a verdict.
Paste addresses from your access log to find out which of the requests claiming to be Googlebot really were.
Common questions
Why is a reverse lookup alone not enough?
Because whoever controls an address block controls its reverse DNS and can point it at any hostname. The forward lookup is what confirms the claim: the hostname must resolve back to the same address, and only the real owner of that hostname can arrange that.
Which hostnames does Googlebot use?
Something ending in googlebot.com or google.com. Anything else claiming to be Googlebot is not, however plausible the user agent looks.
Should I block crawlers that fail this?
Consider it for ones consuming real resources. Bear in mind that a legitimate visitor also fails — the check confirms crawlers, and everybody else is simply not one.
Why does an address resolve to nothing?
Most addresses have no reverse record at all. Residential and mobile ranges usually have none, or a generic one from the provider. That is normal and says nothing about the visitor.