Version 2.1.5 (Apr. 13, 2022)


  1. Added an experimental feature: multi-contact convex collision detection, activated by an enable flag. See full description here.

Bug fixes

  1. GLAD initialization logic on Linux now calls dlopen to load a GL platform dynamic library if a *GetProcAddress function is not already present in the process’ global symbol table. In particular, processes that use GLFW to set up a rendering context that are not explicitly linked against (this applies to the Python interpreter, for example) will now work correctly rather than fail with a gladLoadGL error when mjr_makeContext is called.

  2. In the Python bindings, named indexers for scalar fields (e.g. the ctrl field for actuators) now return a NumPy array of shape (1,) rather than (). This allows values to be assigned to these fields more straightforwardly.

Version 2.1.4 (Apr. 4, 2022)


  1. MuJoCo now uses GLAD to manage OpenGL API access instead of GLEW. On Linux, there is no longer a need to link against different GL wrangling libraries depending on whether GLX, EGL, or OSMesa is being used. Instead, users can simply use GLX, EGL, or OSMesa to create a GL context and mjr_makeContext will detect which one is being used.

  2. Added visualisation for contact frames. This is useful when writing or modifying collision functions, when the actual direction of the x and y axes of a contact can be important.

Binary build

  1. The _nogl dynamic library is no longer provided on Linux and Windows. The switch to GLAD allows us to resolve OpenGL symbols when mjr_makeContext is called rather than when the library is loaded. As a result, the MuJoCo library no longer has an explicit dynamic dependency on OpenGL, and can be used on system where OpenGL is not present.


  1. Fixed a bug in simulate where pressing ‘[‘ or ‘]’ when a model is not loaded causes a crash.

  2. Contact frame visualisation was added to the Simulate GUI.

  3. Renamed “set key”, “reset to key” to “save key” and “load key”, respectively.

  4. Changed bindings of F6 and F7 from the not very useful “vertical sync” and “busy wait” to the more useful cycling of frames and labels.

Bug fixes

  1. mj_resetData zeroes out the solver_nnz field.

  2. Removed a special branch in mju_quat2mat for unit quaternions. Previously, mju_quat2mat skipped all computation if the real part of the quaternion equals 1.0. For very small angles (e.g. when finite differencing), the cosine can evaluate to exactly 1.0 at double precision while the sine is still nonzero.

Version 2.1.3 (Mar. 23, 2022)


  1. simulate now support cycling through cameras (with [ and ] keys).

  2. mjVIS_STATIC toggles all static bodies, not just direct children of the world.

Python bindings

  1. Added a free() method to MjrContext.

  2. Enums now support arithmetic and bitwise operations with numbers.

Bug fixes

  1. Fixed rendering bug for planes, introduced in 2.1.2. This broke maze environments in dm_control.

Version 2.1.2 (Mar. 15, 2022)

New modules

  1. Added new Python bindings, which can be installed via pip install mujoco, and imported as import mujoco.

  2. Added new Unity plug-in.

  3. Added a new introspect module, which provides reflection-like capability for MuJoCo’s public API, currently describing functions and enums. While implemented in Python, this module is expected to be generally useful for automatic code generation targeting multiple languages. (This is not shipped as part of the mujoco Python bindings package.)

API changes

  1. Moved definition of mjtNum floating point type into a new header mjtnum.h.

  2. Renamed header mujoco_export.h to mjexport.h.

  3. Added mj_printFormattedData, which accepts a format string for floating point numbers, for example to increase precision.


  1. MuJoCo can load OBJ mesh files.

    1. Meshes containing polygons with more than 4 vertices are not supported.

    2. In OBJ files containing multiple object groups, any groups after the first one will be ignored.

    3. Added (post-release, not included in the 2.1.2 archive) textured mug example model:

  2. Added optional frame-of-reference specification to framepos, framequat, framexaxis, frameyaxis, framezaxis, framelinvel, and frameangvel sensors. The frame-of-reference is specified by new reftype and refname attributes.

  3. Sizes of user parameters are now automatically inferred.

    1. Declarations of user parameters in the top-level size clause (e.g. nuser_body, nuser_jnt, etc.) now accept a value of -1, which is the default. This will automatically set the value to the length of the maximum associated user attribute defined in the model.

    2. Setting a value smaller than -1 will lead to a compiler error (previously a segfault).

    3. Setting a value to a length smaller than some user attribute defined in the model will lead to an error (previously additional values were ignored).

  4. Increased the maximum number of lights in an mjvScene from 8 to 100.

  5. Saved XML files only contain explicit inertial elements if the original XML included them. Inertias that were automatically inferred by the compiler’s inertiafromgeom mechanism remain unspecified.

  6. User-selected geoms are always rendered as opaque. This is useful in interactive visualizers.

  7. Static geoms now respect their geom group for visualisation. Until this change rendering of static geoms could only be toggled using the mjVIS_STATIC visualisation flag . After this change, both the geom group and the visualisation flag need to be enabled for the geom to be rendered.

  8. Pointer parameters in function declarations in mujoco.h that are supposed to represent fixed-length arrays are now spelled as arrays with extents, e.g. mjtNum quat[4] rather than mjtNum* quat. From the perspective of C and C++, this is a non-change since array types in function signatures decay to pointer types. However, it allows autogenerated code to be aware of expected input shapes.

  9. Experimental stateless fluid interaction model. As described here, fluid forces use sizes computed from body inertia. While sometimes convenient, this is very rarely a good approximation. In the new model forces act on geoms, rather than bodies, and have a several user-settable parameters. The model is activated by setting a new attribute: <geom fluidshape="ellipsoid"/>. The parameters are described succinctly here, but we leave a full description or the model and its parameters to when this feature leaves experimental status.

Bug fixes

  1. mj_loadXML and mj_saveLastXML are now locale-independent. The Unity plugin should now work correctly for users whose system locales use commas as decimal separators.

  2. XML assets in VFS no longer need to end in a null character. Instead, the file size is determined by the size parameter of the corresponding VFS entry.

  3. Fix a vertex buffer object memory leak in mjrContext when skins are used.

  4. Camera quaternions are now normalized during XML compilation.

Binary build

  1. Windows binaries are now built with Clang.

Version 2.1.1 (Dec. 16, 2021)

API changes

  1. Added mj_printFormattedModel, which accepts a format string for floating point numbers, for example to increase precision.

  2. Added mj_versionString, which returns human-readable string that represents the version of the MuJoCo binary.

  3. Converted leading underscores to trailing underscores in private instances of API struct definitions, to conform to reserved identifier directive, see C standard: Section 7.1.3.


    This is a minor breaking change. Code which references private instances will break. To fix, replace leading underscores with trailing underscores, e.g. _mjModelmjModel_.


  1. Safer string handling: replaced strcat, strcpy, and sprintf with strncat, strncpy, and snprintf respectively.

  2. Changed indentation from 4 spaces to 2 spaces, K&R bracing style, added braces to one-line conditionals.

Bug Fixes

  1. Fixed reading from uninitialized memory in PGS solver.

  2. Computed capsule inertias are now exact. Until this change, capsule masses and inertias computed by the compiler’s inertiafromgeom mechanism were approximated by a cylinder, formed by the capsule’s cylindrical middle section, extended on both ends by half the capsule radius. Capsule inertias are now computed with the Parallel Axis theorem, applied to the two hemispherical end-caps.


    This is a minor breaking change. Simulation of a model with automatically-computed capsule inertias will be numerically different, leading to, for example, breakage of golden-value tests.

  3. Fixed bug related to force and torque sensors. Until this change, forces and torques reported by F/T sensors ignored out-of-tree constraint wrenches except those produced by contacts. Force and torque sensors now correctly take into account the effects of connect and weld constraints.


    Forces generated by spatial tendons which are outside the kinematic tree (i.e., between bodies which have no ancestral relationship) are still not taken into account by force and torque sensors. This remains a future work item.

Code samples

  1. testspeed: Added injection of pseudo-random control noise, turned on by default. This is to avoid settling into some fixed contact configuration and providing an unrealistic timing measure.

  2. simulate:

    1. Added slower-than-real-time functionality, which is controlled via the ‘+’ and ‘-‘ keys.

    2. Added sliders for injecting Brownian noise into the controls.

    3. Added “Print Camera” button to print an MJCF clause with the pose of the current camera.

    4. The camera pose is not reset when reloading the same model file.

Updated dependencies

  1. TinyXML was replaced with TinyXML2 6.2.0.

  2. qhull was upgraded to version 8.0.2.

  3. libCCD was upgraded to version 1.4.

  4. On Linux, libstdc++ was replaced with libc++.

Binary build

  1. MacOS packaging. We now ship Universal binaries that natively support both Apple Silicon and Intel CPUs.

    1. MuJoCo library is now packaged as a Framework Bundle, allowing it to be incorporated more easily into Xcode projects (including Swift projects). Developers are encouraged to compile and link against MuJoCo using the -framework mujoco flag, however all header files and the libmujoco.2.1.1.dylib library can still be directly accessed inside the framework.

    2. Sample applications are now packaged into an Application Bundle called When launched via GUI, the bundle launches the simulate executable. Other precompiled sample programs are shipped inside that bundle (in and can be launched via command line.

    3. Binaries are now signed and the disk image is notarized.

  2. Windows binaries and libraries are now signed.

  3. Link-time optimization is enabled on Linux and macOS, leading to an average of ~20% speedup when benchmarked on three test models (cloth.xml, humanoid.xml, and humanoid100.xml).

  4. Linux binaries are now built with LLVM/Clang instead of GCC.

  5. An AArch64 (aka ARM64) Linux build is also provided.

  6. Private symbols are no longer stripped from shared libraries on Linux and MacOS.

Sample models

  1. Clean-up of the model/ directory.

    1. Rearranged into subdirectories which include all dependencies.

    2. Added descriptions in XML comments, cleaned up XMLs.

    3. Deleted some composite models: grid1, grid1pin, grid2, softcylinder, softellipsoid.

  2. Added descriptive animations in docs/images/models/ :

humanoid particle

Version 2.1.0 (Oct. 18, 2021)

New features

  1. Keyframes now have mocap_pos and mocap_quat fields (mpos and quat attributes in the XML) allowing mocap poses to be stored in keyframes.

  2. New utility functions: mju_insertionSortInt (integer insertion sort) and mju_sigmoid (constructing a sigmoid from two half-quadratics).


  1. The preallocated sizes in the virtual file system (VFS) increased to 2000 and 1000, to allow for larger projects.

  2. The C structs in the mjuiItem union are now named, for compatibility.

  3. Fixed: mjcb_contactfilter type is mjfConFilt (was mjfGeneric).

  4. Fixed: The array of sensors in mjCModel was not cleared.

  5. Cleaned up cross-platform code (internal changes, not visible via the API).

  6. Fixed a bug in parsing of XML texcoord data (related to number of vertices).

  7. Fixed a bug in related to nkey (the number of keyframes).

  8. Accelerated collision detection in the presence of large numbers of non-colliding geoms (with contype==0 and conaffinity==0).


  1. Figure selection type changed from int to float.

  2. Figures now show data coordinates, when selection and highlight are enabled.

  3. Changed mjMAXUIMULTI to 35, mjMAXUITEXT to 300, mjMAXUIRECT to 25.

  4. Added collapsable sub-sections, implemented as separators with state: mjSEPCLOSED collapsed, mjSEPCLOSED+1 expanded.

  5. Added mjITEM_RADIOLINE item type.

  6. Added function mjui_addToSection to simplify UI section construction.

  7. Added subplot titles to mjvFigure.


  1. render_gl2 guards against non-finite floating point data in the axis range computation.

  2. render_gl2 draws lines from back to front for better visibility.

  3. Added function mjr_label (for text labels).

  4. mjr_render exits immediately if ngeom==0, to avoid errors from uninitialized scenes (e.g. frustrum==0).

  5. Added scissor box in mjr_render, so we don’t clear the entire window at every frame.

License manager

  1. Removed the entire license manager. The functions mj_activate and mj_deactivate are still there for backward compabitibily, but now they do nothing and it is no longer necessary to call them.

  2. Removed the remote license certificate functions mj_certXXX.

Earlier versions

For changelogs of earlier versions please see