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Nextcloud Calendar vs Proton Calendar: catalog facts
Nextcloud Calendar	Proton Calendar
Free Free app for Nextcloud servers.	Freemium Free account available, with paid Proton plans and a business version.
Web, Self-hosted	Android, iOS, Web
Calendars stay on your own server CalDAV sync with standard clients	End-to-end encryption of event details Built-in scheduling for booking meetings
Requires a running Nextcloud server Not a standalone app	Requires a Proton account Works best within the Proton ecosystem
Self-hosted	Downloadable app, Web application, Hosted service
Open source	Closed source
License not stated	License not stated
Account needed	Account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

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