Nextcloud is an open source content collaboration platform that provides file sync and sharing, file server capabilities, and groupware functionality as an alternative to proprietary services like Dropbox, Google Suite, and Office 365. It allows for decentralization of data storage across trusted servers using open cloud mesh federation with end-to-end encryption and optional key recovery. Nextcloud supports collaboration across iOS, Android, Mac, Windows, Linux, and through CalDAV/CardDAV integration with email clients and Outlook/Thunderbird plugins.