FolderSync vs Syncthing: Which File Sync Tool Is Better in 2026?

FolderSync and Syncthing are both popular tools for keeping folders in sync, but they solve the problem in fundamentally different ways. FolderSync bridges your Android phone to cloud storage. Syncthing connects devices directly, peer-to-peer, with no server in between.

Choosing between them depends on what you own, where your files live, and how much setup you are willing to do.

What FolderSync does well

FolderSync is purpose-built for Android. It connects a local folder on your phone to a cloud provider — Google Drive, Dropbox, OneDrive, SFTP, WebDAV, and dozens more — and keeps them in sync on a schedule you define.

The setup is straightforward: pick a cloud account, pick a local folder, choose one-way or two-way sync, set a schedule, and forget about it. For someone who already stores everything in the cloud and just needs their Android phone to stay current, it works cleanly.

FolderSync also handles filters, so you can exclude file types or folders you do not want to sync. The Pro version adds tasker integration and removes ads.

What Syncthing does well

Syncthing takes the opposite approach. There is no cloud. Devices find each other through a lightweight discovery server, then transfer files directly between themselves using end-to-end encrypted connections.

This makes Syncthing genuinely private — your files never touch a third-party server. It runs on Windows, macOS, Linux, Android, and FreeBSD, and the software is fully open source with regular security audits.

For a home server setup or a pair of desktops that stay powered on, Syncthing is remarkably reliable. It handles large file sets, versioning, and conflict resolution without any cloud dependency.

Where each one falls short

Neither tool covers every scenario, and the gaps are significant.

FolderSync limitations:

• Android only. There is no iOS, Windows, or Mac version. If you own an iPhone or need to sync a desktop folder, FolderSync cannot help.
• Cloud dependent. Every sync runs through a third-party server. You need a storage account, you are subject to its quotas and privacy policies, and transfers use your upload bandwidth twice — once up, once down.
• No peer-to-peer. Even if your phone and laptop are on the same Wi-Fi, FolderSync still routes through the cloud.

Syncthing limitations:

• iOS is broken. Apple's sandbox suspends background apps, so Syncthing's sync engine stops running when you close the app. Folders go stale, conflicts appear, and the experience is unreliable.
• Both devices must be online. Syncthing is peer-to-peer with no relay by default. If your laptop is asleep when your phone changes a file, the sync waits until both are awake simultaneously.
• Complex setup. Device IDs, folder paths, ignore patterns, and firewall rules add friction that casual users hit immediately.

Side-by-side comparison

When you need what both promise but neither delivers

The pattern is clear: FolderSync is simple but locked to Android and cloud. Syncthing is private and cross-platform but unreliable on iOS and complex to set up.

If you need a folder to stay in sync across an iPhone, a Windows PC, and an Android phone — reliably, in the background, without managing a cloud account — neither tool covers it.

Relaaay is built for exactly this gap. When your devices share a network, files transfer directly over the local connection — no cloud, no upload bandwidth wasted. When they are apart, files route through an encrypted relay so the folder catches up as soon as devices reconnect.

On iOS, Relaaay does not fight the sandbox. It delivers content in a way iOS supports, so your folder stays current without you babysitting a foreground app.

You link a folder once. It stays the same on every device, automatically.

If FolderSync or Syncthing already covers your setup perfectly, keep using it. But if you have hit the wall — the missing iOS support, the cloud dependency, the stale folders — the answer is a tool built to work where they cannot.