System-level filesystem technology.
Application-level simplicity.
SDK components for adding virtual filesystems, file filtering, transparent encryption, file sync, and cloud storage integration to your applications.
Without writing kernel-mode driver code.
Trusted by leading organizations worldwide
Developer Components
What are you building?
Development libraries with everything you need to ship. APIs, drivers, documentation, and samples included.
Create virtual filesystems from any data source
Present any data source as local files and folders: cloud storage, databases, REST APIs, or custom content.
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Mount cloud storage as a local drive, in your application
Programmatically mount cloud & remote storage as local virtual drives: S3, Azure, OneDrive, SharePoint, Google Drive, SFTP, and more.
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Intercept, monitor, and control filesystem operations in real time
Enforce filesystem-level access control and security policies by intercepting filesystem, registry, and process operations in real time.
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Encrypt files transparently. Only trusted processes see the real data.
Enforce file-level encryption policies on any set of files and folders. Authorized processes decrypt on the fly; all others see ciphertext.
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Sync local and remote storage in your application
Bidirectional sync using native OS APIs on Windows, Linux, and macOS. Supports placeholder files and on-demand hydration.
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Embed a complete encrypted filesystem inside a single file
Leverage per-file and whole-vault encryption, compression, journaling, and random read/write access from a single portable file.
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Customize Windows File Explorer. Safely, without crashing it.
Extend Windows File Explorer with virtual folders, context menus, overlay icons, and detail columns. All without risking Explorer stability.
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Capture and filter network packets across platforms
Capture, filter, and modify network packets in real time to build advanced network monitoring, security, and traffic analysis solutions.
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Introducing CBFS Cloud
Cloud storage integration, without the plumbing.
Mount remote storage as a fully functional local drive with a single API call. CBFS Cloud supports ten connection types out of the box: S3-compatible storage, Azure Blob, Azure Files, OneDrive, SharePoint, Google Drive, WebDAV, SFTP, and NFS. Easily expose data in these sources as a mounted drive that is visible to every application on the system.
10+ connection types
S3-compatible, Azure Blob, Azure Files, OneDrive, SharePoint, Google Drive, WebDAV, SFTP, and NFS. One API, consistent behavior across all backends.
Local read/write cache
Files are cached locally for disk-speed reads and writes. Background sync pushes changes to the remote backend without blocking your application.
Simple mount lifecycle
Provide credentials, call Mount(), and the drive appears. Unmount with a single call. No driver installation or system configuration required.
Conflict detection
Built-in conflict detection and resolution for concurrent edits. Configurable policies let your application decide how conflicts are handled.
Why Callback
Professional filesystem components
for production software
Kernel-mode driver development on Windows and macOS is a specialized discipline. It requires deep knowledge of OS internals, strict adherence to platform constraints, extensive testing against OS certification suites, and ongoing maintenance as the OS evolves. Most engineering teams, even strong ones, cannot staff this economically. Callback Technologies has been building and maintaining kernel-mode filesystem and network drivers for over 25 years. We understand the kernel so your team does not have to.
Every CBFS component pairs a professionally developed, rigorously tested kernel-mode driver with a clean user-mode API available in .NET, C++, Java, Python, Go, Rust, Delphi, Qt, and more. Our drivers are validated against Microsoft's own filesystem test suites. Our components handle driver signing, deployment packaging, and version management, all of which are problems that consume significant time and expertise when solved from scratch. You write application logic. We maintain the infrastructure layer it runs on.
Support is direct. When you open a ticket, you reach engineers who work on the products, not a first-line triage team reading from a script. We offer free technical support during evaluation and tiered professional support for production deployments. Our customers range from solo developers to Fortune 500 engineering organizations. The support experience is the same either way.
Built for production.
Proven at scale.
Sony, Box, three AWS product teams, Island Enterprise Browser, Boxcryptor, Mountain Duck, and hundreds of other organizations depend on Callback Technologies components for their filesystem and network infrastructure. MyWorkDrive, our own enterprise file access platform deployed across thousands of organizations worldwide, is built entirely on CBFS Connect.
We have been shipping and maintaining these components since the late 1990s. Products are updated annually, tested against new OS releases before they ship, and supported through direct engineering access. If you are building software that will be in production for years, the vendor behind your infrastructure layer matters.
What customers say
"Outstanding stability and performance. At no time did we have to struggle with device driver or stability issues. Just works."
"CBFS Connect is more mature, more professional and more stable."
See how companies across industries have built production solutions with our SDKs. Read the case studies.
Frequently Asked Questions
Callback Technologies makes component libraries that give developers low-level control over filesystems, storage, and networks, all without writing kernel driver code. The Callback Technologies product line covers virtual filesystem creation, filesystem and registry monitoring, transparent file encryption, cloud sync, Windows Shell extensions, embedded file containers, virtual disk drives, and network packet capture. The company has over 20 years of kernel development experience and is trusted by hundreds of enterprise technology companies worldwide.
Callback Technologies components are used to build virtual drives that expose any data source as a standard filesystem, antivirus and DLP agents that intercept file operations in real time, applications with transparent on-the-fly encryption scoped to specific processes, cloud sync clients with native OS status icons, custom Windows File Explorer extensions, encrypted file containers for DRM or records management, virtual block-level disk drives, and network monitoring or packet filtering tools. All without writing kernel driver code.
No kernel development is required. Each component ships with a pre-built, signed kernel driver that handles all low-level OS communication. Developers work with an event-driven API in user-mode code, implementing callback handlers that fire when filesystem, registry, or network events occur. This keeps application code in familiar, debuggable user space, eliminates the risk of kernel bugs crashing the system, and significantly shortens development time.
All products support .NET with Visual Studio integration included, C++, Java, Python, Rust, Go, and Delphi. CBFS Connect, CBFS Sync, CBFS Vault, and PCAP Filter support Windows, Linux, and macOS. CBFS Filter and CBFS Encrypt are Windows-only due to their minifilter driver architecture. CBFS Vault also supports Android and iOS. Every product ships with sample applications in all supported languages and a fully functional 30-day trial.
CBFS Connect includes a FUSE-compatible API, so existing FUSE knowledge transfers directly, with commercial support and stability hardening added on top. Compared to Dokan, CBFS Connect adds enterprise-grade reliability, active maintenance, and thorough documentation. CBFS Filter is built for scenarios where FileSystemWatcher falls short: high-load reliability, the ability to block or modify operations in flight, and registry and process monitoring alongside filesystem events. PCAP Filter uses the same BPF filter syntax as libpcap and Wireshark, and adds real-time packet modification, drop capabilities, and a consistent API across Windows, Linux, and macOS.
Virtual Drive Applications
Need a ready-made application?
Standalone applications that mount remote or encrypted storage as local drives. No development required. Install, configure, connect.
Callback Drive for SFTP Servers
Access files over SFTP through standard Windows file APIs, without mapping a network share or managing a separate client.
Callback Drive for Amazon S3
Browse, open, and edit files stored in S3 directly from File Explorer. No sync, no local copy, no custom tools.
Callback Drive for Microsoft Azure
Connect to Azure storage and work with your files directly from File Explorer, with no Azure-specific tooling required.
Callback Drive for WebDAV Servers
Access WebDAV-hosted files as if they were stored locally. Compatible with any server that speaks the WebDAV protocol.
Callback Drive for NFS Servers
Access files hosted on any NFS server directly from File Explorer, using standard Windows file APIs without additional client software.
Knowledge Base
Hundreds of technical articles covering implementation patterns, common integration questions, platform-specific behavior, and troubleshooting for every product. Searchable and updated continuously.
Browse articlesDocumentation
Complete API reference, getting started guides, and code samples for every product and every supported language: .NET, C++, Java, Python, Go, Rust, Delphi, Qt, macOS, and more. Available online and bundled with each trial download.
Read the docsExpert Support
Free during your 30-day evaluation. Professional and premium tiers available for production deployments, including guaranteed response times and dedicated engineering access for enterprise teams.
Get supportStart with a free 30-day trial
Every product ships fully functional with no feature restrictions during the trial period. Free technical support is included from day one.