Syncthing
title: Syncthing type: tool created: 2026-05-21 last_updated: 2026-05-21 related: ["radar/techniques/PersonalBackupPipeline", "radar/techniques/DockerSecuritySelfHosting"] sources: ["https://github.com/syncthing/syncthing"] radar_quadrant: Tools radar_ring: Assess radar_position: inner
An open-source, decentralised file synchronisation tool that replicates directories between devices over a direct encrypted peer-to-peer connection, with no central server or cloud account required.
Syncthing identifies devices by cryptographic device IDs (public key fingerprints). Two devices pair by exchanging their IDs; subsequent communication is direct, TLS-encrypted, and authenticated. A relay server is used only when direct connections are not possible (NAT traversal); no file data passes through Syncthing's infrastructure.
Each configured folder has a list of sharing devices. Changes are detected via filesystem watching and propagated to peers in near-real-time. Conflict resolution uses a versioning model: conflicting files are renamed rather than silently overwritten.
LAN sync: Two machines on the same network sync directly. Common use: workstation to NAS, laptop to desktop.
Remote sync via relay: Devices on different networks connect through a Syncthing relay. Useful for syncing a home machine with a remote server or VPS.
Always-on node: A headless Syncthing instance on a VPS or home server acts as a persistent peer, ensuring files are available even when mobile devices are offline.
Syncthing is a sync tool, not a backup tool — it propagates deletions and changes bidirectionally. A deleted file on one device is deleted on all peers. For backup purposes, Syncthing's file versioning feature (keep N versions of changed/deleted files) provides recovery, but it is not a substitute for the 3-2-1 strategy in radar/techniques/PersonalBackupPipeline.
The correct layering: Syncthing handles live replication between devices (local copies); rclone handles one-way archival to cloud storage (offsite copy). The two tools are complementary, not competing.
Syncthing has a web UI on localhost:8384 by default. For server deployments, it runs as a systemd service. Docker images are available. The web UI should be access-controlled — by default it binds to localhost only, which is safe; exposing it on a public interface requires authentication configuration.
Syncthing sits in the Assess ring of the Tools quadrant, at inner position. First studied via the GitHub repository (2023-12-23). The project is mature (10+ years, active development, FOSS) and widely used in the self-hosted community, but it has not been set up or run first-person; third-party maturity does not meet the Trial gate, so it stays at Assess. Inner position reflects a straightforward installation path (single binary or Docker), zero ongoing cost, and direct applicability to any self-hosted setup needing live file replication between devices. Syncthing pairs naturally with the Personal Data Backup Pipeline blip. The gate to Trial is a completed first-person sync configuration covering at least one active data directory across two devices.
