Syncthing review

Syncthing is the strongest answer for keeping folders identical across your own computers. Its site describes it as a continuous file synchronization program that syncs between two or more computers in real time, and its FAQ is explicit that it does not upload your data to the cloud but exchanges it directly between your machines. That design removes storage limits and monthly fees: the only cap is the disks you own. Every connection uses TLS with perfect forward secrecy, and only devices you approve by their cryptographic ID can join. Setup happens in a browser interface, and the project says it works over a LAN and over the internet without fiddling with IP addresses, falling back to volunteer relays that cannot read your data. The trade-offs are real. There is no official iOS app, pairing devices and sharing folders takes more clicks than signing into Dropbox, and a laptop that is switched off cannot hand over its latest edits. For desktops, laptops, a home server or a NAS, it is the best free choice.

Who it is for

People who want continuous, private sync between their own computers and servers at no cost.

Price

Free and open source; the project accepts donations.

Open Source. All source code is available on GitHub
Quoted from the vendor pricing page on November 10, 2026.

Key features

• Continuous sync of any number of folders between two or more devices
• Files stay on your own machines with no central server
• All traffic secured with TLS and perfect forward secrecy
• Each device identified by a cryptographic certificate and approved by you
• Web interface for setup and monitoring on macOS, Windows, Linux, FreeBSD and more

Strengths and weaknesses

• Strength: Completely free with no storage cap because there is no cloud tier
• Strength: Open protocol and open source code
• Strength: Works over a LAN and across the internet without port setup
• Weakness: No official iOS client from the Syncthing team
• Weakness: Device pairing and folder sharing take more steps than a cloud app
• Weakness: A device must be online for others to pull its changes

Key facts

• Price: Free, open source
• Where files live: Only on your own devices
• Encryption: TLS with perfect forward secrecy
• Platforms: macOS, Windows, Linux, FreeBSD, Solaris, OpenBSD

Where it ranks

Syncthing is No. 1 in our Best File Sync Software verdict.