Quick answers to the questions every RL practitioner asks about environments.
What is the best RL environment for beginners?
CartPole-v1 (Gymnasium) — balance a pole on a cart with two discrete actions. Then LunarLander-v3 for shaped rewards and a real solve threshold, and MiniGrid for debugging algorithms in minutes on a laptop.
What are the standard deep RL benchmarks?
The Arcade Learning Environment (57 Atari games) for pixel-based control, the MuJoCo locomotion suite and DeepMind Control Suite for continuous control, and Procgen's 16 procedurally generated games for generalization.
Which RL environments are actively maintained in 2026?
The Farama Foundation stewards Gymnasium, PettingZoo, MiniGrid and the ALE. The rising wave is GPU-native: NVIDIA Isaac Lab and MuJoCo Playground. Archived or stale: OpenAI Retro, DeepMind Lab, NetHack Learning Environment, SMAC.
Gymnasium vs PettingZoo — what's the difference?
Gymnasium is the standard API for single-agent environments. PettingZoo, from the same community, is its multi-agent counterpart — 100+ multi-agent envs behind one unified API.
How do I choose an environment for my project?
Match env to goal and compute: classic control for learning on a laptop, Atari/Procgen for benchmarking, MuJoCo or Isaac Lab for robotics with a GPU, PettingZoo or SMAC for multi-agent research. Or use the env picker above — four questions, one shortlist.