What is WHOIS?
WHOIS is a public service that shows who an IP address (or a domain name) is registered to: the owning organisation, the relevant network range, and a contact to reach in case of abuse. Get My Public IP uses RDAP, its modern successor in a structured format (HTTPS/JSON), more reliable to query than the historical text-based WHOIS.
The 5 regional registries
IP addresses aren't managed by a single global organisation, but split between five regional registries (RIRs), each responsible for a geographic area:
What you'll find in a WHOIS record
A WHOIS/RDAP record generally shows the network range concerned, the holding organisation, the relevant registry, the registration and last-updated dates, as well as a contact for reporting abuse. This last piece of information is the most useful in practice: if an IP is causing you harm (attack, spam), that's the contact to alert.
Ready to give it a try?
Look up a WHOIS record