What it is
Syncthing is a program for continuous file synchronization between devices. Instead of sending data to a central cloud, devices discover each other, establish secure connections, and exchange file changes directly.
It is useful for syncing documents, notes, photos, work folders, or configuration between laptops, servers, desktops, and phones without handing files to a third-party storage provider.
What is inside
The repository contains Go code for synchronization, block exchange, device discovery, the web UI, folder handling, configuration, tests, builds, and documentation. It also covers Docker, building from source, signed releases, and project goals.
A typical flow is to install Syncthing on two devices, exchange device IDs, choose a folder, and approve sharing on both sides. After that, file changes propagate between selected nodes.
Synchronization model
This is not a command but a simple mental model: devices and a shared folder.
Laptop <--> Home Server
Folder: Documents
Mode: two-way synchronization
Access: approved devices onlyStrengths
The strength is data control. There is no required central server, users can build their own device topology, and synchronization runs continuously in the background.
Limits
The limitation is operational responsibility. If all devices are off or misconfigured, there is no magical cloud recovery. Backups, conflicts, disk space, and write permissions still matter.