syncthing

Syncthing is a peer-to-peer file synchronization tool that requires no central server. It syncs data directly between devices, eliminating the need to entrust files to third-party cloud services.

• Peer-to-peer sync with no central server, communicating directly between devices
• TLS encryption for all communications with device ID-based authentication
• Selective sync at the folder level with per-device sharing controls
• Conflict handling with automatic detection and preservation of conflicting file versions
• File versioning retaining previous versions of changed or deleted files
• Cross-platform support for Windows, macOS, Linux, Android, and FreeBSD

Built in Go as a standalone binary requiring no installer, Syncthing is completely open with zero cloud dependency. It provides the strongest data sovereignty guarantees as a Dropbox alternative for privacy-focused users.