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Proton Calendar vs Kolab Now: catalog facts
Proton Calendar	Kolab Now
Freemium Free account available, with paid Proton plans and a business version.	Paid Paid subscription service.
Android, iOS, Web	Web
End-to-end encryption of event details Built-in scheduling for booking meetings	Operated in Switzerland since 2013 Email, calendars, contacts, files and video calls in one account
Requires a Proton account Works best within the Proton ecosystem	Hosted service, not something you run yourself Paid service
Downloadable app, Web application, Hosted service	Web application, Hosted service
Closed source	Closed source
License not stated	License not stated
Account needed	Account 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.