ownCloud
ownCloud web server core (Files, DAV, etc.)
...It enables organizations and individuals to maintain full control over their data by running a personal cloud on their own infrastructure rather than relying on third-party providers. The software supports collaborative workflows by allowing users to upload, organize, and share files through a web interface, desktop sync clients, and mobile integrations. Designed with extensibility in mind, the core platform can be enhanced through apps and plugins that add capabilities such as document editing, authentication methods, and workflow automation. It is widely used in enterprise and privacy-focused environments because it combines open-source transparency with enterprise-grade controls and permissions.