Whoisology - Connected database of whois records and whois history
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.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
ICANN WHOIS - The official ICANN WHOIS search for domain lookups.
JsonWhois.io - JsonWhois is the leading cloud hosted Whois API.
Active Whois Browser - Browse all information for an IP address or domain name with a single click!