Syncthing

What is Syncthing?

Syncthing is an open-source, peer-to-peer file synchronisation tool. Files sync directly between your devices over your local network (or encrypted over the internet) — no third-party cloud storage involved.

It's great for:

• Syncing notes, configs, and documents between machines
• Keeping a NAS in sync with your laptop
• Replacing Dropbox or iCloud for sensitive files you'd rather not hand to a company

Installation

macOS:

Download the latest .dmg from the official GitHub releases page. Mount the DMG and drag Syncthing.app to your /Applications folder.

On first launch, macOS may block the app since it was downloaded outside the App Store. If you see a "cannot be opened because the developer cannot be verified" warning, remove the quarantine attribute:

sudo xattr -rd com.apple.quarantine /Applications/Syncthing.app

Then launch the app normally. Syncthing runs as a tray icon and starts its background process automatically. The web UI will be available at http://localhost:8384.

To start Syncthing automatically at login, open the app and enable Start at Login from the tray menu.

Connecting Two Devices

1. Open the web UI on both devices (http://localhost:8384)
2. On Device A: Actions → Show ID — copy the long device ID
3. On Device B: click Add Remote Device, paste Device A's ID
4. Device A will receive a notification to approve the connection — accept it
5. Share a folder from either device: Add Folder → Sharing tab → select the remote device

Conflict Resolution

Syncthing does not merge files — if the same file is modified on two devices before they sync, it creates a conflict copy named like:

document.sync-conflict-20240512-143022-ABCDEF.txt

The original file keeps the "winning" version (most recent modification time). You resolve conflicts manually.

Ignore Patterns

Create a .stignore file in any shared folder to exclude files:

// Ignore macOS metadata
.DS_Store
.AppleDouble

// Ignore build artefacts
node_modules
dist
*.log

• Lines starting with // are comments
• Prefix a pattern with ! to un-ignore something previously ignored