Syncthing File Synchronization

Syncthing is a free and open-source peer-to-peer file synchronization tool that continuously synchronizes files between two or more devices in real time, without relying on any central server or cloud service. Created by Jakob Borg (calmh) in 2013 and written in Go, Syncthing is designed as a privacy-focused alternative to cloud-based sync services like Dropbox, Google Drive, and OneDrive, transferring data directly between devices over encrypted connections. Key features: peer-to-peer: data is transferred directly between devices over the internet or local network, without passing through any intermediate server. This means no monthly fees, no storage limits, and complete data privacy. End-to-end encryption: all communication between devices is encrypted using TLS 1.3 with mutual certificate-based authentication. Each device generates a unique ECDSA key pair (device ID) on first run. Device pairing: devices are paired by exchanging device IDs (a 52-character string derived from the public key). Only explicitly trusted devices can connect and sync. Selective sync: choose which folders to sync on each device. Individual files within a folder can be marked as needed or not needed, enabling partial sync of large folders. Conflict resolution: when the same file is modified on two devices simultaneously, Syncthing creates a conflict copy (with timestamp) rather than overwriting changes, ensuring no data is lost. Versioning: optional file versioning (trash can, simple, staggered, external) to keep old versions of files for rollback. Block-level sync: only changed blocks (128 KB) are transferred, minimizing bandwidth usage for large files with small changes. Global and local discovery: devices can find each other via global discovery servers, local broadcast (IPv4/IPv6), or static addresses. Relay: optional relay servers facilitate connections between devices behind firewalls or NAT. Cross-platform: Linux, macOS, Windows, Android, BSD, Solaris. MPL-2.0.