LocalSend vs Syncthing: File Transfer or Folder Sync — Which Do You Need?
LocalSend is a manual file transfer tool — you pick files, the other device accepts, and the transfer is done. Syncthing is a continuous folder sync engine that keeps directories mirrored automatically across devices. LocalSend is simpler but cannot watch a folder. Syncthing is more powerful but struggles on iOS and requires both devices to be online at the same time.
LocalSend and Syncthing are two of the most recommended open-source tools for moving files between devices. They are also completely different tools that solve completely different problems — and confusing the two is where most frustration starts.
LocalSend sends files. Syncthing syncs folders. Understanding that distinction saves you from trying to force one tool into the other's job.
What LocalSend does
LocalSend works like AirDrop but across every platform. You open it on two devices that share a network, pick the files you want to send, and the other device gets a prompt to accept. The transfer happens directly over your local network — no server, no account, no internet required.
It is beautifully simple. There is no configuration, no device IDs to exchange, no folder paths to set up. You see a device, you send to it, you are done.
The tradeoff is that simplicity comes from doing less. LocalSend does not watch a folder. It does not run in the background. It does not remember what it sent yesterday. Every transfer is a conscious, manual action.
What Syncthing does
Syncthing is the opposite. You configure two or more devices to share a folder, and from then on, Syncthing watches that folder and propagates every change — new files, edits, deletions — automatically, in real time.
It is peer-to-peer and encrypted, so files never touch a third-party server. The software is open source, heavily audited, and runs on Windows, macOS, Linux, Android, and FreeBSD.
For a pair of desktops or a home server, Syncthing is one of the most reliable sync tools available. The cost is in setup: device IDs, folder configuration, ignore patterns, and firewall rules all need attention before the first file moves.
How they actually compare
| LocalSend | Syncthing | |
|---|---|---|
| Core job | Send files on demand | Sync folders continuously |
| Watches a folder | No | Yes |
| Background operation | No | Yes (except iOS) |
| iOS support | Yes | Unreliable — suspended by sandbox |
| Needs both devices online | Yes (same network) | Yes (simultaneously) |
| Setup complexity | None | High |
| Cloud fallback for remote transfers | No | No (relay servers optional, limited) |
| Privacy | Local network only | End-to-end encrypted P2P |
| Cost | Free | Free |
The table makes the distinction clear: LocalSend is for the moment, Syncthing is for the long run. But neither handles the full picture.
The gap neither one fills
LocalSend cannot sync. If you send a folder through LocalSend on Monday and add three files on Tuesday, those files do not arrive on the other device until you manually send them again. There is no automation, no watching, no background process.
Syncthing can sync, but it struggles where many people need it most:
- iOS is unreliable. Apple's sandbox suspends Syncthing's background process, so folders go stale and conflicts pile up.
- Both devices must be online at the same time. If your phone changes a file while your laptop is asleep, the sync waits. For people who do not leave devices running 24/7, this creates gaps.
- No cloud fallback. When devices are not on the same network and not online together, files are stuck.
So you end up using LocalSend for quick sends because Syncthing is too complex for one-off transfers, and Syncthing for ongoing sync because LocalSend cannot do it — but neither handles iOS well, and neither bridges the gap when devices are apart.
What fills both roles
Relaaay is built for continuous folder sync — like Syncthing — but with the setup simplicity of LocalSend. You link a folder once on each device, and it stays mirrored automatically from then on.
When your devices share a network, transfers happen directly over the local connection — fast, private, no cloud involved. When they are apart, files route through an encrypted relay so the folder catches up as soon as a device reconnects.
On iOS, Relaaay does not rely on a background process that Apple will suspend. It delivers content in a way iOS supports, so your linked folder stays current without you holding the app open.
Keep LocalSend for the quick file toss across the room. For the folder that needs to stay the same on every device, let sync handle it — automatically, in the background, on every platform.