Select the “Mail Plus” or “Proton Unlimited” paid plans for more features.
Reviewed by Gabriel Bachmann
Proton Calendar
proton.me/calendar 4.3 (10)
Rate Proton Calendar: No account needed
Threat level
Covered
A covered pick. Anyone can use it as a private drop-in, with no setup or know-how. Enough for most people. Threat levels
Our take
An end-to-end encrypted calendar where even event details and titles are hidden from the provider, which is rare and genuinely valuable, especially if you already live in the Proton ecosystem. The honest limits are practical: the best features sit behind a paid plan, and a fully encrypted calendar trades away some of the slick sharing and integration you get from Google. Pick it if you treat your schedule as sensitive data. Mainstream convenience seekers may find it more locked-down than they expect.
GitHub at a glance
ProtonMail/WebClients GPL-3.0 monorepopgpprotoncalendarprotoncontactsprotondriveprotonmailreactwebmailyarn
Stars
5,676
+16 this week
Forks
741
168 watching
Last commit
today
healthy
Star history
Issues
67% closed
132
open
268
closed
+6 / -1
opened / closed, last 4 weeks
Opened vs closed, last 12 weeks
Commits, last 26 weeks
17,248 commits, active 25 of 26 weeks
97 contributors since Jun 2016
Languages
- TypeScript 94.8%
- JavaScript 2.1%
- SCSS 1.6%
- Other 1.5%
Updated daily from the GitHub API. Star tracking since Jun 15, 2026.
Website at a glance
proton.me
B+ score 80
Solid website security headers
Graded by Mozilla HTTP Observatory, tested 2d ago
Inspect this site yourself
Measures the security configuration of the tool's own website, not the privacy of the product itself. A strong tool can still score low here.
Proton Calendar alternatives
PrivacyNotes Encrypted notes, tasks, calendar, files, passwords and a journal with mood and medication tracking, all unlocked by one 12-word recovery phrase. Sign up with no email and no password. Open source.
Tuta Tuta: Free, Cross-Platform and Zero-Knowledge Calendar
EteSync If you decide to self-host EteSync you won't have to pay for the subscription. Tutorial here .
SilentSuite End-to-end encrypted sync for calendars, contacts, and tasks, wired into the apps you already use over CalDAV.
Radicale A simple self-hosted CalDAV and CardDAV server for calendars and contacts, written in Python and licensed under GPLv3.
Peergos Audited by Cure53 in May 2019.
Proton Calendar license, in plain English
GPL-3.0 Strong copyleft
Free to use and modify, but anything you distribute that is built on it must also be open under the same license.
Permits
- Commercial use
- Modification
- Distribution
- Patent use
- Private use
Requires
- Disclose source
- Same license
- State changes
- License and copyright notice
Does not provide
- Liability cover
- Warranty
Why it matters: Strong copyleft keeps every distributed version open. A vendor cannot fold this into a closed product and ship it without releasing their changes.
Plain-language summary of the project's license, not legal advice. Read the full text for the exact terms.