Cyberduck is a mature, multi-protocol file transfer client for macOS, Windows, and Linux (CLI). It supports over 30 storage protocols including S3, SFTP, FTP, WebDAV, Azure, Google Drive, Dropbox, Backblaze B2, and many more. The architecture is a Java core library with platform-specific UI bindings: Cocoa for macOS (via Rococoa/JNA), WinForms/WPF for Windows, and a command-line interface (duck). The core defines a clean set of feature interfaces (Read, Write, Find, Delete, etc.) that each protocol module implements, enabling a uniform file operation model. The system also integrates client-side encryption via Cryptomator vaults, which wrap protocol features transparently using decorator patterns. Key external dependencies include Apache HttpClient, JSch (SSH), and various cloud SDKs.