Domain Whois Tool fetches the registered data for the domain from the global whois servers.
Which server does it use?
Domain Whois Tool starts from the IANA whois server (whois.iana.org) and recursive fetches data from whois servers until it finds the authoritative record.
What or Who is IANA?
Internet Assigned Numbers Authority (IANA) is resposible for managing all domain and IP addresses on the Internet. It works with RTRs (Regional Internet Registry) to further delegate and manage all internet resources.
Why are there so many whois servers?
Each TLD (.com, .net, .in) has a responsible authority for managing domain registrations and updates. Some TLDs (.com, .net) have more than one registration authorities and each maintains its own whois server. IANA as worked out a referral mechanism by which whois servers can refer to the authoritative whois server for each TLD.
Does this tool work for all TLDs?
Yes, since this tool uses IANA recommended traversal method it works across all TLDs