How to Use Syncthing: The Beginner's Guide (First Pairing, First Shared Folder, and the LAN-Only Rule)
CodexFuse Team · 2026-10-30T06:58:09.646Z · 11 min read
Syncthing is a free, open-source program that keeps folders identical across your devices — your computer and phone sync directly with each other, with no cloud account, no subscription, and no company holding a copy of your files. If you are tired of your phone and laptop being out of sync, or you do not trust another cloud service with your documents, learning how to use Syncthing is the one skill that fixes both problems. This beginner guide walks you through the whole thing: installing it on two devices, pairing them with a QR code, sharing your first folder, choosing folder types, protecting yourself from accidental deletes, and locking traffic to your local network. If you also want those same devices reachable away from home without opening router ports, our Tailscale beginner guide covers the remote-access side.
What is Syncthing and why would you use it instead of cloud storage?
Syncthing is a continuous file synchronization program that syncs files between two or more computers in real time, safely protected from prying eyes. It is built on a simple idea: your data is your data alone, and you get to choose where it is stored, whether it is shared with a third party, and how it travels over the internet.
Cloud storage does the job, but it puts your files on someone else's servers, behind a monthly fee, and inside an account you must keep paying for. Syncthing skips all three. Files move directly between your devices in encrypted chunks, so nothing ever sits on a company server. The trade-off is honest: you manage your own setup and your own safety net, which is exactly what this guide teaches you to do.
How do I install Syncthing on my computer and phone?
Download the latest release for your operating system from the official downloads page and unpack it; on Debian or Ubuntu you can also install it from the project's own package repository. Windows users get a lightweight installer called Syncthing Windows Setup, Mac users get a ready-made application bundle, and Linux users can often install it straight from their distribution's packages. As of October 2026, the current release is v2.1.7.
On your phone, grab the Android app from your app store — Syncthing officially supports Android alongside Windows, macOS, Linux, and FreeBSD. The first time you launch Syncthing on any device it generates a configuration file and your personal encryption keys, then opens the admin interface in your browser at http://127.0.0.1:8384. That web page is your control panel for everything that follows.
If the raw download feels too bare, the community maintains friendlier wrappers on top of the same Syncthing core: SyncTrayzor for Windows adds a tray icon, filesystem watcher, and launcher. The downloads page lists these integrations as the recommended starting point for new users who do not love the command line.
How do I connect two devices with Syncthing?
Two devices talk only when each one knows the other — and they prove it with device IDs. Follow these steps with both devices in front of you:
- Open the admin panel on your computer at http://127.0.0.1:8384 and look at the right-hand side. You will see one device listed: your own computer. On the left is the folder list, where a "Default Folder" sits marked Unshared for now.
- Show your computer's device ID. Click Actions in the top-right corner, then choose Show ID. You will get a 56-character string and a QR code. The ID is a unique, cryptographically secure identifier generated the first time Syncthing ran.
- Scan it from your phone. Open Syncthing on your phone, go to add a new device, and point the camera at the QR code. The ID field fills in automatically. Give it a friendly name and save.
- Confirm on the other side. Because adding a device goes both ways, your computer will show a prompt asking whether to accept the new device. Accept it, and the two are linked. Repeat the exchange in reverse if the phone needs to be known by the computer first.
- Wait a minute. The new device appears on the right side as disconnected at first, then connects after a short while. Connection changes are not instant, especially after a restart.
One reassuring fact from the official getting-started guide: the configuration must be mutual for a connection to happen, so device IDs do not need to be kept secret. They are essentially part of the public key. Treat the ID like an email address — shareable with the devices you want — not like a password.
How do I share my first folder?
Pairing connects the devices; sharing a folder actually moves files. On your computer, click Add Folder and give it a label, a local path on your hard drive, and a folder ID. That folder ID matters: it must match on every device you want to include, or the sync will not work.
After you add the folder and select your phone as a sharing target, a prompt pops up on the phone asking you to accept the folder and choose where it should live in local storage. The moment you approve it, the two devices compare what they each have and start syncing directly, transferring files in encrypted chunks with no cloud service in the middle. From here on, adding files to the shared directory on either device syncs them to the other side automatically and continuously.
What are Syncthing folder types and which one should I pick?
Not every folder should sync in both directions. Syncthing gives you three folder types, and most beginners can leave the default one alone — but knowing the other two saves you from real accidents later.
| Folder type | What it does | Best for |
|---|---|---|
| Send & Receive | Changes flow both ways — every device stays identical. | Your everyday folders: documents, photos, notes. |
| Send Only | This device's changes win; changes from other devices are ignored. If it drifts out of sync, an "Override Changes" button forces this device's state onto the cluster. | A reference copy that must stay canonical, like a curated media library. |
| Receive Only | Changes from the cluster are applied; local changes are not sent out. A "Revert Local Changes" button undoes any local edits. | Backup destinations and replication mirrors where the local copy should never win. |
Watch the buttons when you use the one-way types: clicking Override Changes on a Send Only folder overwrites the cluster with this device's files — files that do not exist here get deleted everywhere. That is powerful and unforgiving, so confirm before you click.
How does Syncthing stop a stray delete from wiping my files?
A deleted file syncs away just as fast as a saved one — that is the first rule of syncing. Before you use Syncthing for anything important, turn on file versioning in the folder's advanced settings. The moment it is enabled, Syncthing quietly saves a copy of any file just before it gets overwritten or deleted, tucking those older versions into a hidden folder called .stversions.
| Versioning strategy | What it keeps | Best for |
|---|---|---|
| Trash Can | The most recent deleted copy of each file. | Protection against accidental deletes only. |
| Simple | A set number of old versions — for example, the last five before the oldest is dropped. | Everyday documents where a few drafts back is enough. |
| Staggered | Hourly, daily, weekly, and monthly snapshots, thinned over time. | Long projects where history matters, if you can spare the disk space. |
Remember the bigger truth: sync is not backup. Versioning rescues you from mistakes, but if your house floods, every synced device can still lose the same files at once. Real backup still needs a second location, which the off-site section below covers.
How do I keep Syncthing traffic on my local network only?
By default Syncthing uses global discovery and relaying to find your devices across the internet, which is what makes the "it just works" experience possible. If you want everything to stay inside your own network, the switch is simple: open the connection settings and turn off Global Discovery and Enable Relaying. With those off, the software falls back to Local Discovery, which finds your devices on the local network instead of reaching out to the internet.
On a LAN-only setup, devices talk to each other directly over port 22000 (the GUI listens on port 8384, which stays bound to your own machine). If your devices cannot see each other, the official docs point to one culprit first: your firewall. Port 22000 needs to be open between your devices, and if something still fails, the GUI's log messages usually say what the connection is waiting for.
This is the setup the LAN-only rule asks for: no discovery servers, no relays, just your devices on your network. When it matters — say you are syncing tax documents and want zero internet exposure — flip those two switches before you share your first folder.
Can I use Syncthing as an off-site backup?
Honestly: not by itself. Syncthing has no web dashboard you can browse from anywhere, and more importantly it does not give you the automatic off-site redundancy a paid cloud service provides. When your files only live on hardware you physically own, one bad event — a fire, a flood, a theft — could wipe everything out at once.
The good news is you can build the off-site part yourself with spare hardware you probably already own: an old laptop, a Raspberry Pi, or even a cheap external drive hidden somewhere else. Mark that remote device as untrusted and set the shared folder to Receive Encrypted. From that point on, your primary machine scrambles everything locally, and the remote device just stores unreadable noise — if that hardware is ever stolen, whoever has it gets nothing useful without your folder password. If disaster does hit, you pull the encrypted data back down and restore it to a new machine.
Pair this mindset with the rest of the self-hosted toolkit: our Jellyfin beginner guide covers your media library the same way, and our Ollama beginner guide brings AI models to your own hardware with the same keep-it-local philosophy.
Should I use Syncthing or Nextcloud?
They answer different needs. Syncthing syncs folders directly between devices with no server at all; Nextcloud is a full self-hosted cloud platform with file sync, calendars, office apps, and a web dashboard — but it needs a server running 24/7.
| Syncthing | Nextcloud | |
|---|---|---|
| Server needed | No — devices sync peer to peer. | Yes — one machine must host the instance. |
| Setup effort | Low — install, pair IDs, share folders. | Medium — deploy the stack, secure it, maintain it. |
| What you get | Folder sync, versioning, encrypted transfers. | Sync plus calendar, contacts, notes, office editing, sharing links. |
| Cost | Free open-source, no account ever. | Free open-source too, but server hardware and power cost something. |
For most beginners, start with Syncthing when the goal is simply "my files are the same on my computer and phone." Move to Nextcloud when you need the whole office suite and sharing links that come with it. The two can even live together: sync to Nextcloud's data folder with Syncthing and let it serve the web view.
Sources
- Syncthing downloads page (syncthing.net) — checked 30 October 2026: current release v2.1.7, OS integrations (Syncthing Windows Setup, Syncthing macOS bundle, SyncTrayzor v2), Debian/Ubuntu packages.
- Syncthing official documentation: "Getting Started" (docs.syncthing.net) — checked 30 October 2026: device IDs generated at first start, mutual configuration requirement, Actions → Show ID, Add Remote Device on both devices, Default Folder in the home directory, GUI at 127.0.0.1:8384, listeners on port 22000.
- Syncthing official documentation: "Folder Types" (docs.syncthing.net) — checked 30 October 2026: Send & Receive, Send Only (Override Changes), Receive Only (Revert Local Changes) behavior.
- MakeUseOf, "My files sync between every device with no cloud, no account, and no fee" (published 19 June 2026, checked 30 October 2026): 56-character device IDs with QR pairing, LAN-only via disabling Global Discovery and relaying, folder IDs must match on every device, file versioning into the .stversions folder, Trash Can / Simple / Staggered strategies, Receive Encrypted for untrusted devices, sync-is-not-backup warning.
Frequently Asked Questions
Is Syncthing really free?
Yes. Syncthing is open-source and free to use, with no account, no sign-in, and no paid tiers. You only ever pay for your own hardware and electricity.
Does Syncthing work on iPhone?
There is no official iOS app — Syncthing runs on Windows, macOS, Linux, FreeBSD, and Android. iPhone users can sync through a desktop intermediary or use third-party wrappers, but Android pairing is the smooth path covered in this guide.
Do I need to keep my device ID secret?
No. Two devices only connect when each is configured with the other's ID, so the ID works like part of a public key. Share it with the devices you want to sync; what you protect is your admin GUI and folder passwords.
Does Syncthing work without an internet connection?
Yes. With Global Discovery and relaying turned off, devices find each other through Local Discovery on your own network — no internet required at all.
What happens if I delete a file on one device?
The deletion syncs to every device, just like any other change. Turn on file versioning first so the deleted copy is saved into the hidden .stversions folder, and keep a real off-site backup for disasters versioning cannot cover.