TL;DR — Quick Summary

Deploy Syncthing for peer-to-peer file sync without cloud services. Sync folders directly between devices with encryption and conflict resolution.

Why Syncthing?

Cloud sync services own your data. Syncthing syncs directly between your devices:

  • Peer-to-peer — No cloud server, no storage limits.
  • End-to-end encryption — Data encrypted in transit (TLS).
  • File versioning — Keep old versions of changed files.
  • Selective sync — Choose folders and devices.
  • Conflict resolution — .sync-conflict files preserve both versions.
  • Multi-platform — Linux, macOS, Windows, Android.
  • No subscription — Completely free, forever.

Prerequisites

  • Two or more devices.
  • Network connectivity between them (LAN or internet).

Step 1: Install and Pair

# Docker
docker run -d \
  --name syncthing \
  --restart=always \
  -p 8384:8384 \
  -p 22000:22000/tcp \
  -p 22000:22000/udp \
  -v /path/to/sync:/var/syncthing \
  syncthing/syncthing:latest

Web UI at http://device:8384.

Step 2: Sync Patterns

Pattern Setup Use Case
Laptop ↔ Desktop Share device IDs, select folders Same files on both machines
Phone → NAS Android app syncs camera folder Automatic photo backup
Multi-device mesh All devices paired, shared folders Team document sharing
One-way send Send-only on source, receive-only on target Backup archive
Selective folders Different folders per device Work on laptop, media on NAS

File Versioning Options

Type Behavior Best For
Trash can Deleted/replaced files go to .stversions Simple recovery
Simple Keep N old versions Predictable cleanup
Staggered Keep versions at increasing intervals Long-term history
External Run custom script on version Advanced workflows

Syncthing vs Cloud Sync Services

Feature Syncthing Dropbox Google Drive Nextcloud
Architecture P2P (no server) Cloud Cloud Self-hosted server
Privacy E2E, no third party Their servers Their servers Your server
Storage limit Your disk 2 GB free 15 GB free Your disk
Cost Free $12/mo (2 TB) $3/mo (100 GB) Free (self-hosted)
File versioning Built-in 30 days 30 days Built-in
Mobile Android iOS + Android iOS + Android iOS + Android
Offline Full offline Selective Selective Selective

Troubleshooting

Problem Solution
Devices not discovering each other Ensure both are on same network or enable global discovery; check firewall ports 22000/TCP+UDP
Sync slow over internet Enable relaying as fallback; check if UPnP is disabled on router
Conflict files appearing Normal — review .sync-conflict files and keep the correct version
High CPU/disk during initial sync Expected for large folders; will settle after initial sync completes

Summary

  • P2P sync — your files, your devices, no cloud.
  • File versioning with four strategies for different needs.
  • Zero cost, zero limits — sync as much as your disks hold.
  • Works on every platform including Android for photo backup.