WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
ipdata.co - Get the Geolocation, Organisation, Currency, Timezone, Calling Code, Flag, Proxy, Tor and Threat intelligence data from any IPv4 or IPv6 address.
Bulk Whois API - Bulk Whois API is a provider of parsed WHOIS data in JSON with simple API, competitive pricing, top notch support, and more.
ipgeolocation.io - Free IP Geolocation API and Accurate GeoIP Lookup Location Database
Whoisology - Connected database of whois records and whois history
ipinfo.io - Simple IP address information.