The best free Circuit Simulator alternative to Simulink is Circuit JS, which is also Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Simulink and seven of them are free Circuit Simulators so hopefully you can find a suitable replacement. Other interesting free Circuit Simulator alternatives to Simulink are SimulIDE, Ktechlab, OpenModelica and Experimenters Circuits.
Simulink alternatives are mainly Circuit Simulators, but if you're looking for
Electronic Design Automation Tools or IDEs you can filter on that. Other popular filters include
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EU-based alternatives if you prefer software developed in the European Union. These are just examples - use the filter bar below to find more specific alternatives to Simulink.
This only simulates circuits, and while it definitely works for circuits the UI is awkward.