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Celestia vs WorldWide Telescope: catalog facts
Celestia	WorldWide Telescope
Free Free and open source.	Free Free and open source.
Windows, macOS, Linux	Web
Free, real-time 3D exploration of space Move freely between planets, stars and galaxies	Large collection of sky imagery in the browser Guided tours with narration and slides
Project website blocks automated visitors with a proof-of-work check A simulator for exploration rather than a structured astronomy course	Needs a fast internet connection Interface can feel dense for newcomers
Downloadable app	Web application
Open source	Open source
License: GPL-2.0	License not stated
No account needed	Not stated if an account is needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked October 2, 2026

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