Nextcloud

Nextcloud is a comprehensive, self-hosted content collaboration platform that provides file sharing, synchronization, communication, and productivity tools as a fully open-source alternative to proprietary cloud services like Google Workspace, Microsoft 365, and Dropbox. Founded in 2016 by Frank Karlitschek after he left ownCloud (a project he also founded) over disagreements about the direction of the company, Nextcloud has grown into the most widely deployed self-hosted cloud platform, used by over 25 million users worldwide including government agencies, enterprises, educational institutions, and individuals who prioritize data sovereignty and privacy. Key features include: file synchronization and sharing (uploading, downloading, and sharing files across desktop, mobile, and web clients with end-to-end encryption support), calendar and contacts (CalDAV and CardDAV integration for managing calendars, events, tasks, and address books), email (a built-in webmail client with IMAP and SMTP support), video and audio calls (via the Nextcloud Talk app, providing WebRTC-based video conferencing, screen sharing, chat, and SIP bridge integration for telephone calls), collaborative document editing (via the Text app for markdown and the integration with Collabora, ONLYOFFICE, or Nextcloud Office for real-time collaborative editing of documents, spreadsheets, and presentations), task management (via the Tasks app), notes (via the Notes app for quick text notes), password management (via the Passwords app), project management (via Deck, a Kanban board app), and an App Store with over 200 community and enterprise apps for extending functionality. As of 2026, Nextcloud has over 30,000 stars.