Proton Calendar

An end-to-end encrypted calendar from Proton, where Proton says it cannot read your event details.

Instead of Google Calendar

proton.me/calendar

Screenshot from proton.me/calendar, taken 2026-10-30, shown to help you recognise the tool. It belongs to its maker. Ask us to remove it.

Proton Calendar encrypts your event titles, descriptions, locations and attendees end to end, and Proton says not even it can read the details. It also encrypts invitee information so that Proton does not know who is on an invitation, uses Curve25519 elliptic curve cryptography, and signs events so that nobody, Proton included, has altered your events or data history. The web app is fully open source and both apps are described as independently audited, though the page names no auditors.

Proton Calendar scores a 4 on self-direction and delivery and a 3 on footprint, lock-in, power and longevity.

It is one company's service, so a change at Proton changes your calendar, and the page says nothing about whether Proton can see other data such as account information or event timing. When we read it, the Android app's code was not yet public. The page lists no free plan limits, so check the pricing page.

What stands out

• Event details and invitees are encrypted end to end
• The web app is fully open source, and both apps are described as audited
• One company's service, with no free plan limits listed

For comparison, we also reviewed Google Calendar (16/30) as a benchmark.