The present contribution introduces the design, methods, functionalities and capabilities of the open source multibody dynamics code Exudyn, which has been developed since 2019. The code has been designed for rigid and flexible multibody systems, with focus on performance for regular multi-core CPUs. It includes script language based modeling and it is intended to be used in science and education, but also in industry. The open source code is available on GitHub and consists of a main C++ core, a rich Python interface including pre- and post-processing modules in Python,and a collection of rigid and flexible bodies with according joint, load and sensor functionality. Integrated solvers allow explicit and implicit time integration, static solution, eigenvalue analysis and optimization. In the paper, the code design, structure, computational core, computational objects and the multibody formulations are addressed. In addition, the computational performance is evaluated with examples of rigid and flexible multibody systems. The results show the significant effect of multithreading even for comparatively small systems as well as for larger models.