About OpenSim.zip
OpenSim.zip is a library of simulation models you can run, read and take with you. Each model is a working interactive simulation, an explanation of the mathematics behind it, and a small package of code that reproduces it outside the browser.
What the library is for
Search for “random walk simulation” or “M/M/1 queue simulation” and you mostly find code repositories without explanations, explanations without working models, or applets that no longer run. OpenSim.zip puts the pieces on one page: the model running near the top, the equations or rules it follows, what it deliberately leaves out, the code it runs, and a download.
It is written for developers, students in engineering, computer science and statistics, researchers who need a quick reference implementation, and teachers who want a model their students can inspect rather than just watch.
Why “.zip”
The name is literal. Every simulation on the site ships as a .zip package: a README, a model.json describing the parameters, the JavaScript file the page itself runs, a Python port that gives the same numbers for the same seed, example output and an MIT license. Explore a model, inspect how it works, run the code, download the files. The model packages page lists them all.
What is on the site
- Simulations grouped into eight fields, from Monte Carlo methods and stochastic processes to queueing, agent-based models and physics.
- Learn: short method notes shared by many models — random-number generation, Monte Carlo error, time stepping and SimPy.
- Methodology: how the models are implemented, tested and sourced.
Licensing
Code in the model packages and the code excerpts on the pages are released under the MIT License: use them, change them, ship them, keep the copyright notice. The explanatory text and the site design are © 2026 OpenSim.zip.
About the name
OpenSim.zip is an independent library of general simulation models. It is not connected with OpenSim, the musculoskeletal modeling software from Stanford University, or with OpenSimulator, the open-source virtual-world server — two unrelated projects that share part of the name.