The world’s most secure calendar

Proton Calendar is the world’s only calendar that uses end-to-end encryption and cryptographic verification to protect your entire schedule.

Need a secure calendar for work? Discover Proton for Business.

Proton Calendar uses end-to-end encryption to secure your events' details.
Your event details, including location, participants, and description, are securely encrypted.

Secured by strong encryption

A calendar is a record of your life and contacts, and it contains some of your most sensitive online data. Proton Calendar helps you keep it safe automatically.

End-to-end encryption

With Proton Calendar, all of an event’s critical information, like the title, description, location, and attendees, are stored securely and privately with end-to-end encryption. Not even Proton can read your event details. 

Elliptic curve cryptography

Proton Calendar leverages advanced, high-performance elliptic curve cryptography (ECC Curve25519) to secure your data. This happens automatically in the background without requiring any action from you. 

Open source and independently audited

The Proton Calendar web app is fully open source, so the code is available for inspection. Our mobile apps' code will be open sourced next. Our apps have been independently audited to verify that they actually work as advertised.

Keep your event invitations private with Proton Calendar.

Keep participants private

When you invite someone to an event, this information is encrypted so that not even Proton knows their identity. This significantly enhances the anonymity of the participants.

Cryptographic verification

It is possible to invite other people onto a shared Proton Calendar. We utilize a secure invitation protocol that cryptographically certifies that the person inviting you is who they say. If you send the invitation, it also lets the invited member cryptographically verify that it was you who invited them.

The signature of the data cryptographically ensures that each type of data was created and edited by the specified author and guarantees that nobody (not even Proton) has tampered with your events.

This cryptographic verification happens automatically in the background without requiring any action from you.

Images of a calendar event and all the information that Proton Calendar encrypts.