Syncthing

Continuous file synchronization — private, secure, decentralized.

✨ Features

Real-Time Sync — Files are synchronized continuously as they change, with no polling or manual triggers
End-to-End Encrypted — All traffic is secured with TLS and perfect forward secrecy — no third party ever sees your data
Decentralized — No central server. Your data stays on your devices, communicating peer-to-peer
Cross-Platform — Windows, macOS, Linux, FreeBSD, Docker, NAS appliances, Android, and iOS (third-party)
Web UI — Full-featured management interface accessible from any browser
Conflict Handling — Intelligent conflict detection and resolution with version history
Bandwidth Control — Per-folder and per-device rate limiting, scheduling, and traffic management
Discovery — Automatic LAN and WAN discovery via global and local discovery servers
Open Source — MPL-2.0 licensed, 85K+ GitHub stars, battle-tested for over 12 years

🚀 Deploy on Railway

One-Click Deploy

Click the button above to deploy Syncthing instantly on Railway.

Prerequisites

A Railway account

⚙️ Environment Variables

Variable	Required	Default	Description
`PORT`	No	`8384` (set by Railway)	Web UI listen port. Railway injects this automatically; the entrypoint maps it to Syncthing's GUI address.
`PUID`	No	`1000`	User ID for file ownership (only used when running as root)
`PGID`	No	`1000`	Group ID for file ownership (only used when running as root)
`STGUIADDRESS`	No	`0.0.0.0:${PORT}`	Override the GUI listen address (format: `:`)
`STHOMEDIR`	No	`/var/syncthing/config`	Syncthing config directory
`UMASK`	No	—	File creation umask (e.g., `002` for group-writable folders)

🔒 Security Note

Syncthing listens on 0.0.0.0:PORT by default so Railway's health checks and public routing work. Set a GUI password immediately after first login — the Web UI has no default authentication. Go to Actions → Settings → GUI Authentication to configure a username and password.

📡 Service Topology

┌────────────────────────────────────────────────────────────┐
│                     Syncthing Container                      │
│                                                              │
│  ┌────────────┐  ┌──────────────┐  ┌───────────────────┐   │
│  │  Web UI    │  │  Sync Engine │  │  Discovery        │   │
│  │  :8384/PORT│  │  :22000      │  │  :21027/udp       │   │
│  │  REST API  │  │  TCP+UDP     │  │  (global+LAN)     │   │
│  └────────────┘  └──────────────┘  └───────────────────┘   │
│        │                │                                     │
│        │           ┌────┴────┐                                │
│        │           │         │                                 │
│   ┌────┴────┐  ┌──┴──┐  ┌───┴────┐                           │
│   │ Browser │  │ Dev │  │ Remote │                           │
│   │  (Web)  │  │  A  │  │  Dev B │                           │
│   └─────────┘  └─────┘  └────────┘                           │
│                                                              │
│  Storage: /var/syncthing (ephemeral on Railway)              │
│  ┌────────────────────────────────────────┐                  │
│  │  config/  (STHOMEDIR)                   │                  │
│  │  Sync/    (default sync folder)         │                  │
│  └────────────────────────────────────────┘                  │
└────────────────────────────────────────────────────────────┘

💻 Local Development

Prerequisites

Docker installed on your machine

Quick Start

# Clone the repository
git clone https://github.com/INAPP-Mobile/railway-syncthing.git
cd railway-syncthing

# Build and run with Docker
docker build -t syncthing-railway .
docker run -d \
  --name syncthing \
  -p 8384:8384 \
  -p 22000:22000 \
  -p 22000:22000/udp \
  -p 21027:21027/udp \
  -e PORT=8384 \
  -v syncthing-data:/var/syncthing \
  syncthing-railway

# Open the Web UI
open http://localhost:8384

Using Docker Compose

services:
  syncthing:
    build: .
    ports:
      - "8384:8384"
      - "22000:22000"
      - "22000:22000/udp"
      - "21027:21027/udp"
    environment:
      - PORT=8384
      - PUID=1000
      - PGID=1000
    volumes:
      - syncthing-data:/var/syncthing
    healthcheck:
      test: ["CMD", "curl", "-fkLsS", "-m", "2", "http://127.0.0.1:8384/rest/noauth/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 15s

volumes:
  syncthing-data:

🔧 Troubleshooting

Issue	Solution
Health check failing	Ensure `PORT` env var is set correctly. Railway sets it automatically. The health check hits `/rest/noauth/health` on the Web UI port.
Cannot access Web UI	Verify the Railway domain is correct. Check logs for startup errors. The GUI listens on `0.0.0.0:PORT`.
Devices can't connect	Syncthing uses port 22000 (TCP+UDP) for sync traffic. On Railway, only the port in `PORT` is publicly routed. Other devices connect outbound from Syncthing to your devices, or via relay discovery. Configure your devices to use relay connections or ensure they can reach each other directly.
Slow sync speeds	Railway's network topology may prevent direct peer-to-peer connections. Syncthing will automatically fall back to relay connections, which are slower. For best performance, connect devices on the same LAN.
Data loss on restart	Railway provides ephemeral storage. Data persists within the service's filesystem but is not replicated. For important data, set up syncing to a secondary device as backup.
Default folder not created	Set `STFLAGS=--no-default-folder` in env vars if you want to configure folders from scratch in the Web UI.

📚 Resources

Syncthing Documentation — Official docs
Getting Started Guide — First-time setup walkthrough
Syncthing Forum — Community support
GitHub Repository — Source code & issues
Security Page — Security model details

📄 License

This template deploys Syncthing, which is licensed under the MPL-2.0 License. See the LICENSE file for details.

Deploy and Host

About Hosting

This template deploys Syncthing 2.1.1 on Railway using the official Docker image. It provides a self-hosted, private file synchronization server with a browser-based management interface. The deployment maps Railway's PORT environment variable directly to Syncthing's web UI port, ensuring seamless platform health checks and public routing.

Why Deploy

Self-hosting Syncthing gives you full control over your file synchronization infrastructure. Unlike cloud-based file sync services, Syncthing stores your data exclusively on your own devices — there is no central server, no third-party storage, and no data egress fees. You decide where your files live, who can access them, and how they are transmitted. This is ideal for privacy-conscious individuals, small teams, and organizations that need secure, auditable file synchronization without relying on external providers.

Common Use Cases

Private Cloud Sync — Replace Dropbox, Google Drive, or OneDrive with a self-hosted, zero-knowledge alternative
Team Collaboration — Synchronize project files across team members' devices without a central server
Server Backup — Automatically sync backups from one server to another for disaster recovery
Media Library — Keep media collections in sync between a home server and remote devices
Configuration Management — Distribute configuration files across multiple machines

Dependencies for Syncthing

Deployment Dependencies

Railway Account — A free Railway account with sufficient service quota
No External Databases — Syncthing is self-contained with no external dependencies
Ephemeral Storage — Railway provides service-level filesystem storage; no persistent volume plugin is required

_{Built by INAPP-Mobile — Deploy your own private file sync in minutes.}