Compare software

Proton CalendarEteSync
Freemium

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

 Freemium

The hosted service is paid after a free trial; running your own server is free.

Android, iOS, Web Android, iOS, Web, Self-hosted
  • End-to-end encryption of event details
  • Built-in scheduling for booking meetings
  • Zero-knowledge end-to-end encryption
  • Works with existing contact and calendar apps
  • Requires a Proton account
  • Works best within the Proton ecosystem
  • Hosted service requires a paid plan after the trial
  • Desktop apps need the separate DAV bridge
Downloadable app, Web application, Hosted service Downloadable app, Web application, Self-hosted, Hosted service
Closed source Open source
License not stated License not stated
Account needed Account needed
Not stated if it works offline Not stated if it works offline

Checked September 23, 2026

Checked October 1, 2026

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