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Proton Calendar vs Tuta Desktop: catalog facts
Proton Calendar	Tuta Desktop
Freemium Free account available, with paid Proton plans and a business version.	Freemium A free account with limited storage and one address. Paid plans add custom domains…
Android, iOS, Web	Windows, macOS, Linux
End-to-end encryption of event details Built-in scheduling for booking meetings	End-to-end encrypts mail bodies, subject lines, calendar and contacts Password-protected messages to recipients who are not Tuta users
Requires a Proton account Works best within the Proton ecosystem	No IMAP or SMTP, so third-party mail clients cannot be used A Tuta account is required; it is not a general mail client
Downloadable app, Web application, Hosted service	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0
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 September 21, 2026

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