Cemu is a cross-platform Wii U emulator written in C/C++. It emulates the PowerPC-based Espresso CPU and Latte GPU via a dynamic recompiler (IML) and interpreter, and provides high-level emulation (HLE) of Wii U operating system libraries (coreinit, GX2, nn_*, etc.). The architecture is a monolithic desktop application with a wxWidgets GUI, multiple graphics backends (Vulkan, OpenGL, Metal), audio backends (Cubeb, XAudio2, DirectSound), and an abstract input layer supporting various controllers. The core emulation loop loads Wii U game images (WUD, WUX, WUHB), parses RPL modules, and translates PowerPC instructions into native code while rendering graphics via Vulkan/OpenGL/Metal. The codebase also includes a GDB stub for debugging, per-title game profiles, graphic packs for patches, and network service stubs (Miiverse, NIM). It is actively maintained with regular commits and vibrant community contributions.
WiiUDownloader is a cross-platform desktop application written in Go that downloads Wii U games, updates, DLC, and demos directly from Nintendo's CDN servers. It is the primary open-source replacement for the abandoned Wii U USB Helper. The application provides a GTK3-based GUI (via gotk3) on all three major platforms, with a command-line core library. Key features include automatic decryption using embedded common keys and title keys derived from PBKDF2, resume-capable downloads with SHA-256 segment verification via a journal file, hash-tree validation for hashed content, FST/U8 archive extraction, and a queue-based batch download system. The architecture cleanly separates the core download/decryption logic (root package) from the GUI (cmd/WiiUDownloader), with reusable internal format parsers for TMD, FST, and U8. No title keys are required; the system generates tickets and certificates on the fly. The project is actively maintained, with recent commits and CI/CD pipelines producing Windows, macOS, and Linux builds.