LibGens

LibGens is a portable, open-source software library designed to support the development of emulators for Sega-related video game hardware. It provides a reusable core that handles the essential emulation tasks—CPU execution, audio synthesis, video timing, memory mapping, input handling, and save state management—so frontend emulators can share a common foundation rather than reimplementing low-level components.

Historically, LibGens originated from the Gens emulator project and was released as a library version that could be integrated into multiple projects. The library targets several Sega platforms, including the Genesis/Mega Drive, the Master System, the Game Gear, and the Sega CD, enabling consistent behavior across different frontends while preserving system-specific quirks.

Its implementation is cross-platform and written primarily in C and C++, with interfaces designed to be portable to Windows, Linux, macOS, and other environments. The project provided API hooks for ROM loading, controller input, audio output, video rendering, and state save/restore, allowing developers to build complete emulators without duplicating core functionality.

LibGens is distributed under an open-source license (GPL). The project has been associated with preservation of older emulator technology and has influenced or served as a basis for later emulator efforts; however, as with many archival emulation projects, activity has fluctuated over time and newer projects have arisen to replace or supersede its role in some ecosystems.