17 self-hosted Apple iCloud Calendar alternatives

Nextcloud is an open-source content collaboration platform providing file sync & share, groupware (calendar, contacts, mail), real-time office editing, chat and video conferencing.

36.7k stars5.2k forksAGPL-3.0last commit 4 Sept 2026Actively maintained

Lightweight CalDAV/CardDAV server for syncing calendars, to-dos, and contacts with many clients, storing data on the filesystem and supporting auth and TLS.

5k stars522 forksGPL-3.0last commit 3 Sept 2026Actively maintained

Baïkal is a lightweight CalDAV/CardDAV server with a web admin UI for managing users, calendars, and address books, backed by MySQL or SQLite.

3.3k stars316 forksGPL-3.0last commit 13 Aug 2026Actively maintained

Prebuilt Nextcloud appliance and management tools for Raspberry Pi, Odroid, VMs and LXC; includes Apache, PHP, MariaDB, Redis, web panel and backup utilities.

2.9k stars320 forkslast commit 29 Jun 2026Actively maintained

Open source groupware suite providing webmail, calendaring, address books, and shared resources via open standards like IMAP, CalDAV, and CardDAV.

2.2k stars322 forksGPL-2.0last commit 3 Sept 2026Actively maintained

EteSync (Etebase Server) provides a self-hostable, zero-knowledge, end-to-end encrypted sync backend for calendars, contacts, tasks and notes across devices.

1.8k stars102 forksAGPL-3.0last commit 12 Jul 2024Likely dormant

sabre/dav is a PHP framework for building WebDAV file servers and CalDAV/CardDAV calendar and contacts services.

1.7k stars371 forksBSD-3-Clauselast commit 2 Aug 2026Actively maintained

Open-source task scheduler and calendar app that auto-plans tasks, syncs with external calendars, and provides a modern UI for managing time blocks and workflows.

985 stars71 forksMITlast commit 2 Jul 2026Actively maintained

Davis is a sabre/dav-based CalDAV/CardDAV/WebDAV server with a modern Symfony 7 admin dashboard for managing users, calendars, sharing, and address books.

744 stars46 forksMITlast commit 30 Jul 2026Actively maintained

Cyrus IMAP is a secure, scalable mail server providing IMAP/JMAP email plus CalDAV/CardDAV contacts and calendars, with ACLs, quotas, search, and replication.

644 stars174 forkslast commit 3 Sept 2026Actively maintained

Self-hosted Next.js React CalDAV client for managing VTODO tasks and VEVENT calendars with multi-account, list/Gantt/calendar views and filters.

630 stars42 forksGPL-3.0last commit 11 Jul 2026Actively maintained

Lightweight CalDAV/CardDAV server implemented in Python that stores calendars and contacts in a Git-backed hierarchy with history and sync support.

599 stars57 forksGPL-3.0last commit 31 Aug 2026Actively maintained

Open-source, browser-based groupware providing calendar, email, file manager, CRM, projects, Collabora Online integration and SSO support.

295 stars112 forkslast commit 4 Sept 2026Actively maintained

PHP-based groupware and CRM for teams: calendars, contacts, email, file management, projects and CRM with CalDAV/CardDAV/IMAP support and extensible modules.

277 stars58 forksAGPL-3.0last commit 3 Sept 2026Actively maintained

Open-source PHP groupware providing CalDAV/CardDAV, ActiveSync, email client, CRM, tasks, file manager and Docker images for on-premise collaboration.

22 stars4 forksAGPL-3.0last commit 3 Sept 2026Actively maintained

DAViCal is an open source CalDAV/WebDAV calendar server using PostgreSQL, enabling shared calendars, access delegation, and meeting scheduling across many clients.

Activity unknown

Citadel is an open source groupware and messaging server providing email, calendars, contacts, and a web interface with room-based collaboration.

Activity unknown