Syncthing is a free, open-source, peer-to-peer file synchronization tool. See features, platforms, pricing, pros, cons, and FAQs.
Category
File Management
Pricing
free/open-source, from Free
Verified
Not yet
Last updated
July 19, 2026
Founded
2013
Free PlanOpen SourceSelf-Hosted
What Is Syncthing
Syncthing is an open-source, continuous file synchronization program that keeps folders in sync across two or more devices in real time. Unlike cloud storage services, it transfers files directly between devices peer-to-peer, with no central server storing user data.
Syncthing's inception dates to December 15, 2013, and it reached its 1.0 release in 2019 after about five years of beta development. It is maintained by the Syncthing Foundation, a Swedish nonprofit organization, with Kastelo Inc. providing commercial support and additional funding from sponsors such as Mobius Sync and REEF Solutions.
Key Features
Syncthing is built around privacy and security: all data transfers are encrypted with TLS and include perfect forward secrecy, and devices authenticate one another using cryptographic certificates rather than relying on a shared password or central account.
The protocol and source code are fully open and documented on GitHub, and the tool is managed through a browser-based, local web interface designed to require minimal configuration. It runs across a wide range of operating systems, including Windows, macOS, Linux, FreeBSD, Solaris, OpenBSD, Android, and iOS.
Pricing
Syncthing is completely free and open-source software with no licensing fees or commercial tiers for the core product. Kastelo Inc. offers separate commercial support services for organizations that want professional assistance, but running Syncthing itself costs nothing.
Key Features
Peer-to-peer synchronization — Transfers files directly between devices without routing data through a central server.
No central server required — Files stay under user control on the participating devices rather than in a third-party cloud.
TLS-encrypted transfers — Secures all data in transit with TLS encryption and perfect forward secrecy.
Certificate-based device authentication — Uses cryptographic certificates to control which devices are trusted to sync.
Open protocol and source — The Block Exchange Protocol and full source code are publicly documented and available on GitHub.
Broad platform support — Runs on Windows, macOS, Linux, FreeBSD, Solaris, OpenBSD, Android, and iOS.
Browser-based web interface — Managed through a local web UI designed to work with minimal setup.
Continuous sync — Monitors folders and syncs changes automatically as files are added or modified.
Pros & Cons
Pros
Completely free and open-source with no paid tiers
True peer-to-peer design with no central server storing data
Strong encryption and certificate-based device authentication
Wide platform support across desktop and mobile operating systems
Backed by a nonprofit foundation with commercial sponsor support
Cons
No built-in cloud backup, since it syncs between devices rather than to a remote server
Initial setup of device pairing can be less intuitive than consumer cloud sync tools
Relies on devices being online simultaneously for real-time sync between them
No official enterprise-managed dashboard beyond community and Kastelo support offerings
Conflict resolution for simultaneous edits requires manual review
Pricing
Open source (only option) Free one-time setup, self-managed
Frequently Asked Questions
Is Syncthing free
Yes, Syncthing is completely free and open-source software with no paid tiers.
Does Syncthing use a central server
No, Syncthing synchronizes files directly between devices using a peer-to-peer protocol, with no central server storing data.
What platforms does Syncthing support
Syncthing runs on Windows, macOS, Linux, FreeBSD, Solaris, OpenBSD, Android, and iOS.
Who maintains Syncthing
Syncthing is maintained by the Syncthing Foundation, a Swedish nonprofit, with commercial support from Kastelo Inc. and other sponsors.
When was Syncthing created
Syncthing's inception dates to December 15, 2013, with its 1.0 release arriving in 2019.
Is Syncthing secure
Yes, all data transfers are encrypted using TLS with perfect forward secrecy, and devices authenticate using cryptographic certificates.
What language is Syncthing written in
Syncthing is written in Go.
Can Syncthing sync files over the internet, not just a local network
Yes, Syncthing can sync files between devices on a local network or remotely over the internet.