What an IP lookup can and cannot tell you
An IP lookup answers three questions well: which organisation the address block is registered to, which autonomous system announces it to the internet, and roughly where that network operates. Those come from public routing data and registry records, which is why they are reliable and free.
It answers a fourth question badly: who the person behind the address is. Anyone promising a name or a street address from an IP alone is selling a guess.
This page therefore shows what is verifiable — network, operator, reverse name, coarse location — and labels the rest as an estimate.
ASN, ISP and organisation: three different names
The AS number is the identity of a network in the global routing table. It is the single most stable fact about an address, because routing has to agree on it for packets to arrive at all.
The ISP field is the retail provider. The organisation field is whoever registered the block, which for cloud addresses is the cloud provider, not the customer running the server.
When the three disagree, trust the AS number first. Registry records go stale; routing does not.
How accurate is IP geolocation?
Country-level accuracy is high because address blocks are allocated per region and providers rarely move them across borders. City-level accuracy is a different story.
Treat the coordinates as the centre of a region, never as an address. When the answer matters, corroborate it with a second signal such as the reverse DNS name or the observed network latency.
VPNs, corporate proxies and satellite links break city accuracy entirely; that is their purpose.
Reverse DNS and forward-confirmed reverse DNS (FCrDNS)
A reverse lookup asks the DNS for a PTR record under in-addr.arpa or ip6.arpa and returns a hostname. Only the operator that holds the address block can publish that record, which is what makes it meaningful.
Forward-confirmed reverse DNS takes the PTR name and resolves it again, checking that it points back to the original address. Passing that round trip proves the same party controls both directions.
- No PTR at all is normal for home connections and most cloud instances. It only becomes a problem when that host sends mail.