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OpenRDAP vs WhoisThisDomain: catalog facts
OpenRDAP	WhoisThisDomain
Free Free and open source under the MIT License.	Free Freeware from NirSoft, free to use and redistribute unmodified.
Windows, Linux, Command line	Windows
Supports domain, IP, autonomous system, nameserver, and entity queries. Outputs results as text or JSON, with WHOIS-style output for domain queries.	Chooses the WHOIS server automatically by TLD Batch lookups and name-and-extension combinations
Limitations not stated	Only queries WHOIS servers on port 43, not web-based WHOIS Proxy authentication with a user name and password is not supported
Downloadable app	Downloadable app
Open source	Closed source
License: MIT	License: Freeware
Not stated if an account is needed	No account needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked October 6, 2026	Official website Full listing and sources Checked October 8, 2026

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