Private. None of your data is ever stored anywhere else other than on your computers. There is no central server that might be compromised, legally or illegally.
Encrypted. All communication is secured using TLS. The encryption used includes perfect forward secrecy to prevent any eavesdropper from ever gaining access to your data.
Authenticated. Every device is identified by a strong cryptographic certificate. Only devices you have explicitly allowed can connect to your other devices.
Powerful. Synchronize as many folders as you need with different people or just between your own devices.
Portable. Configure and monitor Syncthing via a responsive and powerful interface accessible via your browser. Works on Mac OS X, Windows, Linux, FreeBSD, Solaris, OpenBSD, and many others. Run it on your desktop computers and synchronize them with your server for backup.
Simple. Syncthing doesn’t need IP addresses or advanced configuration: it just works, over LAN and over the Internet. Every machine is identified by an ID. Give your ID to your friends, share a folder and watch: UPnP will do if you don’t want to port forward or you don’t know how.