Gymnasium

Gymnasium is the community-maintained fork of OpenAI Gym, serving as the definitive interface for developing and comparing reinforcement learning (RL) algorithms in 2026. Managed by the Farama Foundation, it provides a standardized Markov Decision Process (MDP) interface that decouples the learning agent from the simulation environment. Its technical architecture is designed for high-performance research, supporting a wide array of environments ranging from classic control tasks and Box2D physics to complex robotics simulations via MuJoCo. As of 2026, Gymnasium has evolved to include native JAX-compatible functional environments and improved vectorized environment support, allowing researchers to scale simulations across thousands of CPU or GPU cores simultaneously. It remains the essential middleware for AI researchers and engineers, ensuring that RL models remain portable, reproducible, and compatible with modern deep learning frameworks like PyTorch, TensorFlow, and JAX. The platform's ecosystem is bolstered by specialized wrappers for reward shaping, observation filtering, and frame stacking, making it the most versatile tool for training agents in both discrete and continuous action spaces.