Sync local filesystems any cloud or remote source.
CBFS™ Sync lets you keep local folders synced with cloud storage or any remote repository, complete with native OS sync icons.
USE CASES
What you can build with CBFS Sync
Build event-driven, cross-platform sync between local folders and a remote backend.
Cloud storage sync clients
Build a OneDrive-style sync client for your own storage backend, with native OS icons and status indicators users already know.
Bi-directional sync with any repository
Keep a local folder synced both ways with a remote repository, database, or service, reacting to local changes in real time.
Cross-platform sync from one codebase
Ship the same sync logic on Windows, Linux, and macOS with one API instead of separate integrations for CfAPI, FUSE, and File Provider.
Real-time local change monitoring
Catch file and folder changes on the local machine as they happen and trigger your own sync, backup, or processing logic.
HOW IT WORKS
One sync API. Three native platform backends.
CBFS Sync wraps each OS's native sync infrastructure, Cloud Filter API on Windows, FUSE on Linux, File Provider on macOS, behind one consistent API.
An event-driven model lets your app watch local files and folders in real time, so changes sync as they happen instead of on a polling schedule.
Because CBFS Sync builds on the same infrastructure as Microsoft OneDrive, synced files show native icons and status indicators users already recognize.
START BUILDING
Documentation & Resources
Online Documentation
Full API reference for all components and languages, with code examples for every method and event.
Read now
Knowledge Base
Troubleshooting guides, how-tos, and answers to common implementation questions.
Read nowCBSync
A step-by-step guide to setting up CBSync and using it to build bidirectional file synchronization between local and remote storage.
Read nowSample Applications
Shows how to synchronize a local folder to another locally accessible folder using the asynchronous mode.
Shows how to synchronize a local folder to another locally accessible folder.
Shows how to synchronize a local folder to another locally accessible folder on macOS.
FEATURES
Comprehensive Features for Maximum Flexibility
Local Folder Monitoring
Local Folder Monitoring
CBFS™ Sync monitors local folders for changes and initiates the synchronization process when changes are detected, firing events as necessary.
Asynchronous Operation
The CBFS™ Sync API is asynchronous by nature, simplifying development and allowing for high efficiency synchronization operations.
Cross-Platform
CBFS™ Sync currently runs on Windows (Intel and ARM), Linux, and macOS. Support for mobile platforms (iOS and Android) is in active development.
Unified API
CBFS™ Sync wraps CfAPI on Windows, FileProvider on macOS, and FUSE on Linux with an easy-to-use intuitive API, simplifying and streamlining development.
PLATFORMS
Supported Languages & Operating Systems
Every edition ships with a pre-built driver, sample applications, and full documentation. 30-day fully functional trial for all editions.
CBFS Sync supports .NET Framework 4.0+ and .NET 5 through .NET 10, with full Visual Studio integration and C# sample applications.
Documentation
CBFS Sync ships 32-bit and 64-bit Windows DLLs and C++ libraries built for Linux and macOS, with no external runtime dependencies.
Documentation
CBFS Sync provides Java classes built on the same high-performance codebase as our native editions, with full Javadoc and seamless integration into IntelliJ and Eclipse.
Documentation
CBFS Sync ships as Python 3 modules for Windows, Linux, and macOS, installable via PIP with comprehensive HTML documentation and sample applications.
Documentation
CBFS Sync ships as Rust crates built on 32-bit and 64-bit shared libraries for Windows, Linux, and macOS, with support for x86/x64 and ARM.
Documentation
CBFS Sync provides high-performance Go packages built on the same C++ codebase as our native editions, supporting Go 1.13+ on Windows, Linux, and macOS.
Documentation
CBFS Sync provides native Delphi VCL components built on our shared codebase, supporting every Delphi version from Delphi 6 through RAD Studio 13.
Documentation
CBFS Sync ships as 32-bit and 64-bit Windows DLLs and C++ libraries for Linux, macOS, and FreeBSD, supporting Qt 4.8, Qt 5, and Qt Creator integration.
Documentation
CBFS Sync ships as a modern XCFramework for macOS, built for native Swift 5 and Objective-C development with full support for Intel and Apple Silicon in Xcode 13+.
DocumentationFAQ
Frequently Asked Questions
Common questions about licensing, integration, and deployment.
What is CBFS Sync?
CBFS Sync is a cross-platform SDK for bidirectional file sync between local filesystems and cloud storage or other remote repositories. It uses the same OS-level sync infrastructure as Microsoft OneDrive: Cloud Filter API on Windows, File Provider on macOS, FUSE on Linux.
Apps built with CBFS Sync show native OS sync status icons, the same experience users expect from built-in sync tools. The backend connection is entirely up to you. CBFS Sync handles the local sync layer and fires events when changes need to go out.
How do I build a cloud sync client with native OS sync icons on Windows, macOS, and Linux?
CBFS Sync gives you this out of the box. Since it wraps the same platform APIs as OneDrive and other first-party sync clients, apps built with it show native sync status icons, syncing, synced, error, with no extra UI work.
Implement event handlers that fire on local folder changes, then push those changes to whatever remote storage you're using. CBFS Sync manages local sync state, OS integration, and event dispatch. The backend can be anything your app can reach.
What OS-level sync infrastructure does CBFS Sync use?
CBFS Sync wraps three platform-native technologies under one API: Cloud Filter API (CfAPI) on Windows, File Provider on macOS, and FUSE on Linux. Same APIs used by Microsoft OneDrive and other first-class sync clients.
Using these instead of polling or filesystem watchers means sync events come reliably from the OS, status icons integrate natively into the shell, and behavior matches what users expect on each platform, no platform-specific code required.
How does CBFS Sync differ from CBFS Connect?
CBFS Connect creates virtual drives where files don't physically exist on disk. Your app serves file contents on demand. Files look real to the OS, but there's no local copy unless your app writes one.
CBFS Sync is for when files genuinely need to exist locally and stay synced with a remote source. It manages that local-to-remote relationship with OS-native sync APIs and gives you the native status icons users expect from a sync client. Need a mounted drive with no local persistence? Use CBFS Connect. Need local files kept in sync with a remote store? Use CBFS Sync.
Which platforms does CBFS Sync support?
CBFS Sync supports Windows (Intel and ARM), Linux, and macOS. iOS and Android support is in active development. Available in .NET, C++, Java, Python, Rust, Go, Delphi, Qt, and native macOS bindings, with Visual Studio integration and samples for every language.
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Built for production. Proven at scale.
Components and drivers from Callback Technologies have been shipping in commercial products for over two decades, from single-developer tools to enterprise software deployed at Fortune 500 companies.
This is a fantastic product, not only is it easy to use, but it's also extremely powerful. It allows you to focus on the business objective of your project rather than the sometimes daunting, intricacies of connectivity and data delivery.
We tried your demos and modified them according to our requirements. As far as we have come with our testing, we were very pleased with the way your component works - compact easy installation, well-done demos, good VCL integration and proper documentation.