I Built an Open-Source Simulink Alternative That Runs in Your Browser

Milan — Mon, 16 Feb 2026 09:24:02 +0000

What if you could build and simulate block-diagram models in your browser — for free, with no installation?

That's what I've been working on for the last 27 months.

The Problem

System simulation — control systems, vehicle dynamics, signal processing — is dominated by MATLAB/Simulink. It's excellent software, but:

Expensive: €2,000-15,000 per seat per year
Closed: Proprietary file formats, vendor lock-in
Heavy: Complex installation, license servers, IT involvement
Isolated: Awkward Python integration, poor CI/CD support

There's no real open-source equivalent at the system simulation level.

The Solution: PathSim + PathView

PathSim is a pure-Python framework for dynamical system simulation:

pip install pathsim

from pathsim import Simulation, Connection
from pathsim.blocks import Integrator, Amplifier, Adder, Scope

# Build a simple feedback system
integrator = Integrator()
gain = Amplifier(-1.5)
summer = Adder()
scope = Scope()

sim = Simulation(
    blocks=[integrator, gain, summer, scope],
    connections=[
        Connection(summer, integrator),
        Connection(integrator, gain),
        Connection(integrator, scope),
        Connection(gain, summer[1])
    ]
)

sim.run(duration=10.0)
scope.plot()

PathView is a visual block-diagram editor that runs entirely in your browser via Pyodide/WebAssembly:

Try it now: view.pathsim.org

No signup. No server. Your data never leaves your machine.

Key Features

18+ numerical solvers — from basic Euler to implicit BDF for stiff systems
Hierarchical subsystems — compose complex models from reusable components
Event handling — hybrid continuous/discrete systems (check the bouncing ball)
Algebraic loop resolution — automatic detection and solving
Browser execution — full simulation in WebAssembly (Pyodide), no backend needed

Real-World Adoption

JSBSim (NASA's flight dynamics simulator) adopted PathSim for system-level modeling
MIT Plasma Science & Fusion Center uses PathSim for nuclear fusion fuel-cycle simulation
300+ GitHub stars, 3,000+ monthly downloads

Python in WebAssembly vs. Server Side

Running a simulation framework in the browser via Pyodide is interesting. You might assume that a dedicated backend serever hosted somewhere on the web wins over Pyodide. But it turns out, when you have a decently performant CPU, the 30% loss of Pyodide over antive Python still places you way ahead of off the shelf server performance.

What's Next

Model library — 50+ curated, validated simulation models
Code generation — C code from PathSim models (early stage)

Try It

Browser editor: view.pathsim.org
Install: pip install pathsim
Docs: docs.pathsim.org
GitHub: github.com/pathsim

I'd love to hear your feedback. What simulation problems are you working on? What would make PathSim useful for your work?

I'm Milan Rother, a simulation engineer. If you need help with simulation — from Simulink migration to custom model development — reach out at milanrother.com.

DEV Community: Milan