---
title: Calendar Sync
icon: material/calendar
description: Calendars contain some of your most sensitive data; use products that implement encryption at rest.
cover: calendar.webp
---

<small>Protects against the following threat(s):</small>

- [:material-bug-outline: Passive Attacks](basics/common-threats.md#security-and-privacy ""){.pg-orange}
- [:material-server-network: Service Providers](basics/common-threats.md#privacy-from-service-providers ""){.pg-teal}

**Calendars** contain some of your most sensitive data; use products that implement end-to-end encryption at rest to prevent a provider from reading them.

## Tuta

<div class="admonition recommendation" markdown>

![Tuta logo](assets/img/email/tuta.svg#only-light){ align=right }
![Tuta logo](assets/img/email/tuta-dark.svg#only-dark){ align=right }

**Tuta** offers a free and encrypted calendar across their supported platforms. Features include automatic E2EE of all data, sharing features, import/export functionality, multifactor authentication, and [more](https://tuta.com/calendar-app-comparison).

Multiple calendars and extended sharing functionality are limited to paid subscribers.

[:octicons-home-16: Homepage](https://tuta.com/calendar){ .md-button .md-button--primary }
[:octicons-eye-16:](https://tuta.com/privacy){ .card-link title="Privacy Policy" }
[:octicons-info-16:](https://tuta.com/support){ .card-link title="Documentation" }
[:octicons-code-16:](https://github.com/tutao/tutanota){ .card-link title="Source Code" }
[:octicons-heart-16:](https://tuta.com/community#donate){ .card-link title="Contribute" }

<details class="downloads" markdown>
<summary>Downloads</summary>

- [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=de.tutao.calendar)
- [:simple-appstore: App Store](https://apps.apple.com/app/id6657977811)
- [:simple-github: GitHub](https://github.com/tutao/tutanota/releases?q=Calendar)
- [:fontawesome-brands-windows: Windows](https://tuta.com/blog/desktop-clients)
- [:simple-apple: macOS](https://tuta.com/blog/desktop-clients)
- [:simple-linux: Linux](https://tuta.com/blog/desktop-clients)
- [:simple-flathub: Flathub](https://flathub.org/apps/com.tutanota.Tutanota)
- [:octicons-browser-16: Web](https://app.tuta.com)

</details>

</div>

## Proton Calendar

<div class="admonition recommendation" markdown>

![Proton](assets/img/calendar/proton-calendar.svg){ align=right }

**Proton Calendar** is an encrypted calendar service available to Proton members via its web or mobile clients. Features include automatic E2EE of all data, sharing features, import/export functionality, and [more](https://proton.me/support/proton-calendar-guide).

Those on the free tier have access to 3 calendars, whereas paid subscribers can create up to 25 calendars. Extended sharing functionality is also limited to paid subscribers.

[:octicons-home-16: Homepage](https://proton.me/calendar){ .md-button .md-button--primary }
[:octicons-eye-16:](https://proton.me/calendar/privacy-policy){ .card-link title="Privacy Policy" }
[:octicons-info-16:](https://proton.me/support/calendar){ .card-link title="Documentation" }
[:octicons-code-16:](https://github.com/orgs/ProtonMail/repositories?q=calendar){ .card-link title="Source Code" }

<details class="downloads" markdown>
<summary>Downloads</summary>

- [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=me.proton.android.calendar)
- [:simple-appstore: App Store](https://apps.apple.com/app/id1514709943)
- [:octicons-browser-16: Web](https://calendar.proton.me)

</details>

</div>

In 2021, Securitum [audited](https://proton.me/community/open-source#:~:text=Proton%20Calendar) Proton Calendar's web client and provided a [letter of attestation](https://res.cloudinary.com/dbulfrlrz/images/v1714639870/wp-pme/letter-of-attestation-proton-calendar-20211109_3138998f9b/letter-of-attestation-proton-calendar-20211109_3138998f9b.pdf) for the Android app.

## Criteria

**Please note we are not affiliated with any of the projects we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements to allow us to provide objective recommendations. We suggest you familiarize yourself with this list before choosing to use a project, and conduct your own research to ensure it's the right choice for you.

### Minimum Qualifications

- Must sync and store information with E2EE to ensure data is not visible to the service provider.

### Best-Case

Our best-case criteria represents what we would like to see from the perfect project in this category. Our recommendations may not include any or all of this functionality, but those which do may rank higher than others on this page.

- Should integrate with native OS calendar and contact management apps if applicable.
