How to set up continuous syncing between two computers using Syncthing
This guide helps you create a reliable, continuous file sync between two computers using Syncthing. It walks through installation, device pairing, folder selection, and practical settings so your files stay mirrored in near real time. Expect to spend about 20–45 minutes to set up and test an initial sync.
Step 1: Install Syncthing on both machines
Download and install the Syncthing build for each operating system (Windows, macOS, Linux) from the official release page or package manager. Use the stable channel and install the service/daemon so Syncthing can run at startup; on Windows enable the service during installation, on macOS use Homebrew with brew install --cask syncthing or run the binary, and on Linux install via your distro package or the tarball. Allow 5–10 minutes for installation and initial configuration.
[Illustration: Two desktop screens showing Syncthing installer windows on Windows and macOS with installation progress bars]
Step 2: Start the Syncthing GUI and secure access
Launch Syncthing; it opens a local web GUI at http://localhost:8384 by default. Set a strong GUI password and, if available, enable HTTPS with a self-signed certificate for remote GUI access. This prevents accidental configuration changes and secures the interface if you access it from outside the machine. Allocate 5 minutes for GUI security settings.
[Illustration: Laptop browser window with Syncthing web GUI and a password field highlighted]
Step 3: Find and exchange device IDs
On each machine, copy the 64-character Device ID from the GUI (top-right or Settings > Device ID) and exchange it with the other machine using a secure channel (email, encrypted chat, or QR code). On each GUI, click Add Device, paste the other Device ID, give it a clear name, and optionally restrict allowed folders. Exchanging IDs typically takes 2–5 minutes and prevents accidental connections.
[Illustration: Two device panels showing long Syncthing Device IDs being copied and pasted between machines]
Step 4: Create and share a folder to sync
On the primary machine, click Add Folder, choose a folder path (recommend a dedicated folder, e.g., C:\Sync or /home/user/Sync), set Folder ID and label, and enable 'Shared With' for the other device. Set File Versioning if you want backups (keep 10 revisions or 30 days). Large folders (over 10 GB) may take hours to initial sync, so consider an initial network transfer via external drive for very big data.
[Illustration: File browser selecting a folder labeled Sync, with Syncthing Add Folder dialog showing folder ID and versioning options]
Step 5: Accept folder share and set path on second machine
On the second computer, a popup will appear to add the shared folder; choose a local path for the copy and verify Folder ID matches. Select whether to 'Download' or 'Receive Only' (choose Receive Only to avoid accidental deletions propagating back). Confirm and let Syncthing scan the folder; initial scanning duration depends on number of files—expect 1–2 minutes for thousands of small files, longer for many GBs.
[Illustration: Second laptop showing Syncthing dialog Accept Share with local path selection and Receive Only checkbox]
Step 6: Verify initial sync and resolve conflicts
Open the GUI on both machines and check folder status: use the 'Out of sync' count and Recent Items list. If conflicts appear, Syncthing appends .sync-conflict-<timestamp> to conflicted files—manually merge or choose the preferred file. For large syncs, monitor transfer rates in the GUI and allow 1–24 hours depending on bandwidth and size.
[Illustration: Syncthing status panel showing synced folder with green Synced badge and recent transfer activity chart]
Step 7: Tune performance and enable auto-start
Adjust settings: set Maximum Concurrent File Requests to 8–16, Limit Network Bandwidth if on metered connections, and enable Global Discovery and Local Discovery for automatic peer detection. Configure Syncthing to run as a system service so it starts automatically; test by rebooting both machines and confirming folders re-sync within 1–2 minutes. Fine-tuning reduces CPU and network spikes while keeping sync continuous.
[Illustration: Syncthing advanced settings window with concurrency and bandwidth sliders and a checkbox for run as service]
- Use a dedicated sync folder rather than system folders to avoid permission issues and accidental deletions.
- For initial large datasets (>50 GB), copy data on a USB 3.0 or SSD to the other machine and then let Syncthing verify, saving hours of network transfer time.
- Set File Versioning to Simple File Versioning with 10 copies for most users, or use Staggered File Versioning for long-term retention; this prevents data loss from accidental edits.
- If you have many small files, enable block-level delta (default) and consider increasing the scan interval to 10–30 minutes to reduce CPU usage.
- Enable NAT traversal and Global Discovery only if both machines are on different networks; for LAN-only sync, disable global discovery for privacy.
- Label devices clearly (e.g., Alice-Laptop, Office-Desktop) and use folder labels that include ownership or purpose to avoid confusion during multi-device setups.
- Do not enable 'Introducer' on a device unless you want it to automatically share all its folders with new peers — this can expose folders unintentionally.
- Avoid placing OS system folders (Program Files, /etc, C:\Windows) into Syncthing; syncing system files can corrupt your OS or cause boot failures.
- On metered or limited connections, set bandwidth limits and test with a small folder first to prevent large unexpected data charges.
- Be careful with 'Send Only' versus 'Receive Only' settings: incorrect direction can cause irreversible deletions to propagate across devices.
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