MuJoCo (Multi-Joint dynamics with Contact) is a high-performance, open-source physics engine designed for accurate and efficient simulation of articulated systems. Developed originally by Emo Todorov and later maintained by DeepMind and Google, MuJoCo is widely used in AI research, robotics, and biomechanics for tasks involving control, motion planning, and reinforcement learning.

MuJoCo excels at simulating continuous control environments, making it a go-to platform for training and evaluating reinforcement learning algorithms. Its real-time performance and precision make it suitable for both academic and industrial applications.

Key benefits include:

• Realistic physics modeling with soft and rigid body dynamics

• Fast and differentiable simulation, ideal for learning and optimization

• Open-source and actively maintained by the research community

What are the main features of MuJoCo?

Accurate multibody dynamics and contact modeling

MuJoCo simulates complex multibody systems with friction, soft contacts, and constraints, using advanced physics solvers.

• Supports rigid and soft bodies, tendons, and joints

• Realistic modeling of contacts, collisions, and actuators

• Engineered for stability even in stiff or constrained systems

Real-time simulation with high performance

The engine is optimized for speed and can simulate thousands of steps per second, enabling large-scale training and experimentation.

• Real-time physics at high frame rates

• Efficient memory and computation for multi-agent scenarios

• GPU acceleration via MuJoCo’s Vulkan-based renderer

Differentiable simulation for learning and control

MuJoCo supports automatic differentiation, allowing gradients to be computed through the physics simulation—a key feature for model-based learning.

• Useful for optimization, system identification, and trajectory planning

• Enables differentiable physics in deep learning pipelines

• Compatible with frameworks like JAX and TensorFlow

Flexible modeling and extensibility

Users can define robots and environments via XML model descriptions or programmatically through APIs.

• MJCF (MuJoCo XML) for declarative environment specification

• Python bindings (mujoco and dm_control) for integration with ML workflows

• Plugin architecture for rendering and custom actuators

Broad adoption in AI and robotics research

MuJoCo powers many of the benchmark environments in reinforcement learning (e.g., OpenAI Gym, DM Control Suite) and is widely used in academic papers.

• Standard for continuous control tasks (e.g., locomotion, manipulation)

• Used by top labs for sim-to-real transfer and embodied AI research

• Open-source under Apache 2.0 since 2021

Why choose MuJoCo?

• Highly accurate and stable physics engine, trusted in control and robotics

• Designed for AI and ML applications, with differentiability and high speed

• Supports complex articulated systems, from humanoids to manipulators

• Integrated into major RL frameworks, enabling fast experimentation

• Open and extensible, backed by Google and an active research community