Nextcloud

Nextcloud is a suite of client-server software for creating file hosting services and using them.

Nextcloud is the most deployed alternative to Office365.

Nextcloud offers the most comprehensive, deeply integrated on-premises collaboration platform on the market, replacing dozens of other tools.

Secure file exchange within and between organizations
Collaborative editing of docx, xlsx and more
File versioning, restore and retention control
Commenting on files, adding notes to share links
Integrated chat and secure audio-video calls
Calendar, mail and task management tools
Comprehensive set of security capabilities

Self hosted on private servers
100% open source
A single, integrated platform
Integration in infrastructure
Security and encryption

Nextcloud is open source – there are no limitations and you can inspect, integrate, extend and modify Nextcloud however you want.