freeglut

FreeGLUT is a free, open-source alternative to the OpenGL Utility Toolkit (GLUT). It provides a cross-platform API for creating windows with OpenGL rendering contexts, handling input devices, and managing simple user interfaces such as menus and timers. Built as a replacement for GLUT, FreeGLUT aims to be source-compatible with GLUT, allowing existing GLUT programs to be compiled and run with minimal changes, while offering additional features and bug fixes.

The library exposes functions to create and destroy windows, query and set window attributes, register callback functions for display, reshape, keyboard and mouse events, and manage the main event loop. FreeGLUT also adds features not present in the original GLUT, such as the ability to exit the main loop programmatically (glutLeaveMainLoop) and an explicit event-driven main loop (glutMainLoopEvent). It continues to implement a broad subset of GLUT's API and often extends it with platform-specific improvements.

FreeGLUT is cross-platform, with native backends for Windows (WGL), X11-based Linux/UNIX environments (GLX), and macOS (CGL/NSGL). It relies on common OpenGL clients such as Mesa or vendor drivers and works alongside many windowing toolkits and development environments.

The project is community-maintained and released under an open-source license (commonly MIT-style). It remains widely used in educational resources and hobbyist projects where rapid OpenGL prototyping is desired, and serves as a drop-in replacement for GLUT in many existing codebases.