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WhoisThisDomain vs ICANN Lookup: catalog facts
WhoisThisDomain	ICANN Lookup
Free Freeware from NirSoft, free to use and redistribute unmodified.	Free Free public lookup service run by ICANN.
Windows	Web
Chooses the WHOIS server automatically by TLD Batch lookups and name-and-extension combinations	Run by ICANN rather than a registrar or advertiser Uses RDAP instead of scraping WHOIS
Only queries WHOIS servers on port 43, not web-based WHOIS Proxy authentication with a user name and password is not supported	Only shows registration data, with no DNS or mail diagnostics
Downloadable app	Web application
Closed source	Closed source
License: Freeware	License not stated
No account needed	Not stated if an account is needed
Needs internet	Needs internet
Official website Full listing and sources Checked October 8, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.