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WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
ViewDNS.info - Free DNS related tools including Reverse IP Lookup, DNS Propagation Checker, Chinese Firewall Test...
Whoisology - Connected database of whois records and whois history
Whois extractor - Whois Extractor provides complete domain database services along with domain owner name, email and phone number. Start trial plan today
JSON WHOIS API - Parsed domain WHOIS data from any WHOIS server via RESTful API with metered pay as you pricing.