LogicSim is an educational tool to help learn about logic gates like AND, NOR, XOR and the others. You can build up simple circuits or more complex circuits, wire up switches and LEDs, and simulate what happens when you interact with it. You can then make things more complicated by adding clocks, counters, encoders, displays and flip-flops.
The aim is to make this available for recreational use and also potentially for use in schools too. I understand that previous versions have been used in school settings, but a lot of changes have been made since then and some work is required to get it back into a deliverable state again.
Full credit to all the previous authors, especially to the creator Andreas Tetzl who started the whole project LogicSim. He nurtured it from its Amiga beginnings to its Java Applets with version 2.4.
After some years in the wilderness, it was reborn on Github as LogicSim3 by Peter 'codepiet' Gabriel, and gained many new functions and a pdf manual, with help from Jens Borsdorf and Matthew Lister. Then in 2025, Benkralex took on the challenge and made a variety of improvements and fixes.
Which brings us to 2026, and I'm now doing some refactorings, bringing the text tokens into a form where the Translatinator can be used, and identifying Issues for any interested parties to help discuss.
The first example shows designing a circuit, with a few logic gates wired together and linked up to three differently-coloured LEDs. The second picture shows simulation of a simpler circuit, using tri-state output gates and a selector switch. The third shows an empty window in beginner mode with lots of simplifications for the first lesson, and the fourth example shows an experiment with percussive beats.
(1) Main screen, showing an example circuit
(2) Simulating a circuit with 3 buttons and 2 tri-state gates
(3) Beginner mode with simplified interface and German language
(4) Using a clock and counter to simulate percussion
The main changes since version 2.4 are the much nicer graphics, a zoom function, rotatable gates, autowiring and a much clearer menu on the left. The main changes I've made with version 3.10 include a major reorganisation of the tokens, allowing the Translatinator to be used make corrections and additions easier. Also the variable "complexity" of the component list and toolbar is new, allowing a more gentle introduction in the classroom. The documentation has been reworked with new screenshots, and several bugs have been fixed (some of which are documented as closed issues on github). The gate mirroring function and the Print option were removed, toolbar buttons for zoom in/out were added, and a new "disconnect" function from the right-click menu. More bug fixes are on the way.
The help pages inside the program are currently only available in English and German (contributions in other languages welcome!). For accessibility these pages are reproduced here as well, in the form of the English help and die deutsche Anleitung.
The source code is at Github, including all its history since 2020.
This zip file contains the current state of the runnable code, just unpack the zip into a new directory and then run the jar from there: LogicSim-3.10-20260328.zip.