Look up an IP address's version, whether it's public or private, and its reverse DNS hostname.
Frequently asked questions
Private IPs (like 192.168.x.x or 10.x.x.x) are only reachable within a local network; global/public IPs are routable on the internet — this is different from whether the address is actually assigned to anyone right now.
It's the hostname associated with an IP address (the reverse of a normal domain-to-IP lookup) — not every IP has one set up, so this may come back empty.