How to Self-Host Syncthing: Peer-to-Peer File Sync 2026

TL;DR

Syncthing (MPL 2.0, ~63K GitHub stars, Go) is a peer-to-peer file synchronization tool — files sync directly between your devices with no central server required. It's like Dropbox but without the cloud: each device keeps a full copy, changes sync in both directions, and everything is encrypted in transit. Use it to sync your documents between laptop and desktop, backup your phone photos to a home server, or keep config files in sync across servers. Dropbox charges $9.99/month for 2TB; Syncthing is free.

Key Takeaways

• Syncthing: MPL 2.0, ~63K stars — P2P file sync, no cloud, end-to-end encrypted
• No central server: Devices sync directly — no cloud storage needed
• Full copies everywhere: Every device has a complete copy of the shared folder
• Conflict resolution: Handles simultaneous edits with conflict files
• iOS/Android: Official apps for mobile devices
• Relay network: Falls back to relay servers when direct connection isn't possible

---

Syncthing vs Dropbox vs Nextcloud

Feature	Syncthing	Dropbox Free	Nextcloud
License	MPL 2.0	Proprietary	AGPL 3.0
Cost	Free	Free (2GB) / $9.99/mo	Free (hosting)
Architecture	P2P (no server)	Centralized cloud	Centralized (self-hosted)
Storage limit	Disk size	2GB / 2TB	Disk size
Mobile backup	Yes	Yes	Yes
File versioning	Yes (configurable)	Yes	Yes
Web UI	Yes (local)	Yes	Yes
Selective sync	Yes	Yes	Yes
End-to-end encryption	Yes	No	Optional
Share with others	Between devices	Yes	Yes

---

Part 1: Docker Setup (Server/Always-On Node)

Run Syncthing on a server as an always-on sync hub:

# docker-compose.yml
services:
  syncthing:
    image: syncthing/syncthing:latest
    container_name: syncthing
    restart: unless-stopped
    hostname: my-syncthing
    ports:
      - "8384:8384"    # Web UI
      - "22000:22000"  # Protocol communication (TCP + UDP)
      - "21027:21027/udp"  # Local discovery
    volumes:
      - syncthing_config:/var/syncthing
      - /path/to/sync:/data    # Synced folder
    environment:
      PUID: 1000
      PGID: 1000
      TZ: America/Los_Angeles

volumes:
  syncthing_config:

docker compose up -d

Visit http://your-server:8384.

---

Part 2: HTTPS with Caddy

sync.yourdomain.com {
    basicauth {
        admin $2a$14$hash_here    # caddy hash-password
    }
    reverse_proxy localhost:8384
}

Or set a username/password directly in the Syncthing web UI: Actions → Settings → GUI.

---

Part 3: Desktop Installation

macOS / Windows / Linux

1. Download from syncthing.net/downloads
2. Run — a tray icon appears
3. Web UI opens at http://localhost:8384

macOS with Homebrew:

brew install syncthing
brew services start syncthing

Linux:

# Add repo and install:
sudo apt install syncthing

# Start as user service:
systemctl --user enable syncthing
systemctl --user start syncthing

---

Part 4: Pair Devices

Syncthing uses Device IDs (like MFZWI3D-BOZGW26-YMWUJ3I-...) for pairing.

On Device A (your server):

1. Web UI → Actions → Show ID
2. Copy the Device ID

On Device B (your laptop):

1. Web UI → Add Remote Device
2. Paste Device A's ID
3. Set a name: My Server

Repeat in reverse — both devices must add each other.

---

Part 5: Sharing Folders

After devices are paired:

On Device A:

1. Add Folder
2. Folder path: /data/documents
3. Folder label: Documents
4. Sharing tab → enable sharing with Device B
5. Save

On Device B:

1. A notification appears: "Device A wants to share folder 'Documents'"
2. Accept → choose local path (e.g., ~/Documents/Synced/)
3. Sync begins immediately

---

Part 6: Folder Types

Type	Behavior
Send & Receive	Full bidirectional sync (default)
Send Only	Changes go out but don't come in — good for archive/backup source
Receive Only	Only receives changes — good for backup destination

Use Receive Only on your server to create a one-way backup:

• Laptop: Send & Receive
• Server: Receive Only

Now the server mirrors the laptop but can't send changes back.

---

Part 7: Mobile Apps

Android

1. Install Syncthing-Fork from F-Droid (recommended) or Syncthing from Play Store
2. Open → Device ID → copy
3. Add on your server's web UI → paste ID
4. Create/accept a shared folder

Auto-sync phone photos:

1. Add Folder: /storage/emulated/0/DCIM/Camera
2. Share with your server
3. Server receives all new photos automatically

iOS

1. Install Möbius Sync (iOS Syncthing client, ~$3)
2. Or use Syncthing for iOS via TestFlight

---

Part 8: Versioning (File History)

Keep old versions of changed/deleted files:

1. Edit Folder → File Versioning
2. Versioning types:
   • None: No versioning (default)
   • Trash Can: Deleted files move to .stversions/ — like a local trash
   • Simple: Keep N versions per file
   • Staggered: More versions for recent changes, fewer for old ones
   • External: Run a script when a file is versioned

Staggered example:
  Files changed today: keep all versions
  Files changed this week: keep 1/day
  Files changed this month: keep 1/week
  Files older: keep 1/month

---

Part 9: Ignore Patterns

Don't sync certain files:

# .stignore (place in the folder being synced)
# Syntax similar to .gitignore

*.tmp
*.log
.DS_Store
Thumbs.db
node_modules/
.git/

The .stignore file itself syncs across devices so all devices use the same rules.

---

Part 10: Relay Servers

When devices can't connect directly (NAT/firewall), Syncthing uses relay servers as a fallback. The data is still encrypted end-to-end — relays only forward encrypted traffic.

To configure your own relay (for privacy or performance):

# Relay server (separate container):
services:
  syncthing-relay:
    image: syncthing/relaysrv:latest
    restart: unless-stopped
    ports:
      - "22067:22067"
      - "22070:22070"

In Syncthing settings, add your relay URL.

---

Maintenance

# Update Syncthing:
docker compose pull
docker compose up -d

# Logs:
docker compose logs -f syncthing

# Check sync status via API:
curl http://localhost:8384/rest/db/status?folder=FOLDER_ID \
  -H "X-API-Key: $(cat ~/.config/syncthing/config.xml | grep -o 'apikey>[^<]*' | cut -d'>' -f2)"

# Backup config:
tar -czf syncthing-config-$(date +%Y%m%d).tar.gz \
  $(docker volume inspect syncthing_syncthing_config --format '{{.Mountpoint}}')

Why Self-Host Syncthing?

The case for self-hosting Syncthing comes down to three practical factors: data ownership, cost at scale, and operational control.

Data ownership is the fundamental argument. When you use a SaaS version of any tool, your data lives on someone else's infrastructure subject to their terms of service, their security practices, and their business continuity. If the vendor raises prices, gets acquired, changes API limits, or shuts down, you're left scrambling. Self-hosting Syncthing means your data and configuration stay on infrastructure you control — whether that's a VPS, a bare metal server, or a home lab.

Cost at scale matters once you move beyond individual use. Most SaaS equivalents charge per user or per data volume. A self-hosted instance on a $10-20/month VPS typically costs less than per-user SaaS pricing for teams of five or more — and the cost doesn't scale linearly with usage. One well-configured server handles dozens of users for a flat monthly fee.

Operational control is the third factor. The Docker Compose configuration above exposes every setting that commercial equivalents often hide behind enterprise plans: custom networking, environment variables, storage backends, and authentication integrations. You decide when to update, how to configure backups, and what access controls to apply.

The honest tradeoff: you're responsible for updates, backups, and availability. For teams running any production workloads, this is familiar territory. For individuals, the learning curve is real but the tooling (Docker, Caddy, automated backups) is well-documented and widely supported.

Server Requirements and Sizing

Before deploying Syncthing, assess your server capacity against expected workload.

Minimum viable setup: A 1 vCPU, 1GB RAM VPS with 20GB SSD is sufficient for personal use or small teams. Most consumer VPS providers — Hetzner, DigitalOcean, Linode, Vultr — offer machines in this range for $5-10/month. Hetzner offers excellent price-to-performance for European and US regions.

Recommended production setup: 2 vCPUs with 4GB RAM and 40GB SSD handles most medium deployments without resource contention. This gives Syncthing headroom for background tasks, caching, and concurrent users while leaving capacity for other services on the same host.

Storage planning: The Docker volumes in this docker-compose.yml store all persistent Syncthing data. Estimate your storage growth rate early — for data-intensive tools, budget for 3-5x your initial estimate. Hetzner Cloud and Vultr both support online volume resizing without stopping your instance.

Operating system: Any modern 64-bit Linux distribution works. Ubuntu 22.04 LTS and Debian 12 are the most commonly tested configurations. Ensure Docker Engine 24.0+ and Docker Compose v2 are installed — verify with docker --version and docker compose version. Avoid Docker Desktop on production Linux servers; it adds virtualization overhead and behaves differently from Docker Engine in ways that cause subtle networking issues.

Network: Only ports 80 and 443 need to be publicly accessible when running behind a reverse proxy. Internal service ports should be bound to localhost only. A minimal UFW firewall that blocks all inbound traffic except SSH, HTTP, and HTTPS is the single most effective security measure for a self-hosted server.

Backup and Disaster Recovery

Running Syncthing without a tested backup strategy is an unacceptable availability risk. Docker volumes are not automatically backed up — if you delete a volume or the host fails, data is gone with no recovery path.

What to back up: The named Docker volumes containing Syncthing's data (database files, user uploads, application state), your docker-compose.yml and any customized configuration files, and .env files containing secrets.

Backup approach: For simple setups, stop the container, archive the volume contents, then restart. For production environments where stopping causes disruption, use filesystem snapshots or database dump commands (PostgreSQL pg_dump, SQLite .backup, MySQL mysqldump) that produce consistent backups without downtime.

For a complete automated backup workflow that ships snapshots to S3-compatible object storage, see the Restic + Rclone backup guide. Restic handles deduplication and encryption; Rclone handles multi-destination uploads. The same setup works for any Docker volume.

Backup cadence: Daily backups to remote storage are a reasonable baseline for actively used tools. Use a 30-day retention window minimum — long enough to recover from mistakes discovered weeks later. For critical data, extend to 90 days and use a secondary destination.

Restore testing: A backup that has never been restored is a backup you cannot trust. Once a month, restore your Syncthing backup to a separate Docker Compose stack on different ports and verify the data is intact. This catches silent backup failures, script errors, and volume permission issues before they matter in a real recovery.

Security Hardening

Self-hosting means you are responsible for Syncthing's security posture. The Docker Compose setup provides a functional base; production deployments need additional hardening.

Always use a reverse proxy: Never expose Syncthing's internal port directly to the internet. The docker-compose.yml binds to localhost; Caddy or Nginx provides HTTPS termination. Direct HTTP access transmits credentials in plaintext. A reverse proxy also centralizes TLS management, rate limiting, and access logging.

Strong credentials: Change default passwords immediately after first login. For secrets in docker-compose environment variables, generate random values with openssl rand -base64 32 rather than reusing existing passwords.

Firewall configuration:

ufw default deny incoming
ufw allow 22/tcp
ufw allow 80/tcp
ufw allow 443/tcp
ufw enable

Internal service ports (databases, admin panels, internal APIs) should only be reachable from localhost or the Docker network, never directly from the internet.

Network isolation: Docker Compose named networks keep Syncthing's services isolated from other containers on the same host. Database containers should not share networks with containers that don't need direct database access.

VPN access for sensitive services: For internal-only tools, restricting access to a VPN adds a strong second layer. Headscale is an open source Tailscale control server that puts your self-hosted stack behind a WireGuard mesh, eliminating public internet exposure for internal tools.

Update discipline: Subscribe to Syncthing's GitHub releases page to receive security advisory notifications. Schedule a monthly maintenance window to pull updated images. Running outdated container images is the most common cause of self-hosted service compromises.

Troubleshooting Common Issues

Container exits immediately or won't start

Check logs first — they almost always explain the failure:

docker compose logs -f syncthing

Common causes: a missing required environment variable, a port already in use, or a volume permission error. Port conflicts appear as bind: address already in use. Find the conflicting process with ss -tlpn | grep PORT and either stop it or change Syncthing's port mapping in docker-compose.yml.

Cannot reach the web interface

Work through this checklist:

1. Confirm the container is running: docker compose ps
2. Test locally on the server: curl -I http://localhost:PORT
3. If local access works but external doesn't, check your firewall: ufw status
4. If using a reverse proxy, verify it's running and the config is valid: caddy validate --config /etc/caddy/Caddyfile

Permission errors on volume mounts

Some containers run as a non-root user. If the Docker volume is owned by root, the container process cannot write to it. Find the volume's host path with docker volume inspect VOLUME_NAME, check the tool's documentation for its expected UID, and apply correct ownership:

chown -R 1000:1000 /var/lib/docker/volumes/your_volume/_data

High resource usage over time

Memory or CPU growing continuously usually indicates unconfigured log rotation, an unbound cache, or accumulated data needing pruning. Check current usage with docker stats syncthing. Add resource limits in docker-compose.yml to prevent one container from starving others. For ongoing visibility into resource trends, deploy Prometheus + Grafana or Netdata.

Data disappears after container restart

Data stored in the container's writable layer — rather than a named volume — is lost when the container is removed or recreated. This happens when the volume mount path in docker-compose.yml doesn't match where the application writes data. Verify mount paths against the tool's documentation and correct the mapping. Named volumes persist across container removal; only docker compose down -v deletes them.

Keeping Syncthing Updated

Syncthing follows a regular release cadence. Staying current matters for security patches and compatibility. The update process with Docker Compose is straightforward:

docker compose pull          # Download updated images
docker compose up -d         # Restart with new images
docker image prune -f        # Remove old image layers (optional)

Read the changelog before major version updates. Some releases include database migrations or breaking configuration changes. For major version bumps, test in a staging environment first — run a copy of the service on different ports with the same volume data to validate the migration before touching production.

Version pinning: For stability, pin to a specific image tag in docker-compose.yml instead of latest. Update deliberately after reviewing the changelog. This trades automatic patch delivery for predictable behavior — the right call for business-critical services.

Post-update verification: After updating, confirm Syncthing is functioning correctly. Most services expose a /health endpoint that returns HTTP 200 — curl it from the server or monitor it with your uptime tool.

---

See all open source file sync and backup tools at OSSAlt.com/categories/storage.

See open source alternatives to Syncthing on OSSAlt.