Syncthing

Syncthing is a continuous file synchronization tool that keeps selected folders in sync between two or more devices. It uses a peer-to-peer model (no mandatory central server), focusing on privacy, resiliency, and cross-platform support for desktops, servers, and mobile devices.

Key Features

• Peer-to-peer folder synchronization between trusted devices (device IDs) without relying on a central storage provider
• Encrypted transport (TLS) and device authentication via cryptographic device identities
• Web-based GUI for configuration/monitoring plus a REST API and event stream for automation/monitoring integrations
• NAT traversal and relay support to connect devices across networks (global discovery and optional relay usage)
• Versioning options for deleted/overwritten files (simple, staggered, trash can, external)
• Per-folder controls: ignore patterns, file/folder permissions handling, rescan intervals, selective folder sharing
• Cross-platform binaries and packaging for common OSes; runs well on headless servers

Use Cases

• Sync a “working files” directory between a laptop and a home server without using Dropbox/Drive
• Keep a replicated copy of important folders across multiple machines as a lightweight redundancy layer
• Maintain shared folders between a small number of trusted devices (e.g., family/workstations)

Limitations and Considerations

• It is not a multi-user collaboration/groupware platform; sharing is based on explicitly trusted device pairs
• Conflicts can occur with concurrent edits; Syncthing creates conflict copies rather than merging content

Syncthing fits users who want direct device-to-device synchronization with strong transport security and operational transparency. It’s especially useful when you want cloud-like syncing behavior while keeping storage and control on your own devices.