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Proton CalendarKashCal
Freemium

Free account available, with paid Proton plans and a business version.

 Free

Free and open source with no ads.

Android, iOS, Web Android
  • End-to-end encryption of event details
  • Built-in scheduling for booking meetings
  • iCloud calendar sync on Android
  • Works with Nextcloud, Fastmail and other CalDAV servers
  • Requires a Proton account
  • Works best within the Proton ecosystem
  • Android only
  • Calendar only, no task or contact management in the app
Downloadable app, Web application, Hosted service Downloadable app
Closed source Open source
License not stated License: Apache-2.0
Account needed No account needed
Not stated if it works offline Not stated if it works offline

Checked September 23, 2026

Checked October 2, 2026

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