CircuitSim alternative: digital logic in the browser, from transistors up
CircuitSim is a free digital circuit simulator by Roi Atalla (ra4king on GitHub), who wrote it out of frustration with Logisim's bugs, quirky interface and lack of continued development. It is a Java desktop application (Java 8 at minimum) with many built-in components: gates, wires and subcircuits, a clock, RAM and ROM with editors, a transistor, a 7-segment display, and a breakpoint component that stops the clock at a chosen value. Circuits can be exported as images, the source is on GitHub under the BSD 3-Clause license, and the latest release is version 1.9.1, from January 2023. CircuitSim is a lean desktop replacement for Logisim; digiwleea is a browser lab that starts at the transistor and teaches its way up to a CPU.
What CircuitSim is good at
Fast, no-nonsense digital design in the Logisim style: wire gates and subcircuits, build memory with RAM and ROM, and debug clocked designs by letting the breakpoint component stop the clock at the value you are looking for. If your course hands out CircuitSim files, use CircuitSim for them. (digiwleea is an independent project, not affiliated with CircuitSim or its author.)
How digiwleea is different
digiwleea runs in any browser with nothing to install and no Java, and it starts one level lower: you wire NMOS and PMOS transistors as switches into NOT and NAND gates, then build adders, latches, registers, RAM and an 8-bit CPU that runs a stored program, through a 40+ level course where every part is checked against its truth table, with an AI tutor (Wleea). Each finished stage becomes a part you reuse in the next. digiwleea cannot open CircuitSim files. For Logisim-style circuits there are also browser options for Logisim users and the Logisim comparison.
| CircuitSim | digiwleea | |
|---|---|---|
| Runs in | Java desktop app (Java 8 or later) | Any modern browser, nothing to install |
| Starts from | Gates and built-in components | CMOS transistors, then gates |
| Memory | RAM and ROM components | RAM you build, plus the course's memory levels |
| Learning path | Your course's assignments | 40+ level course + theory lessons, AI tutor |
| Price | Free, open source (BSD 3-Clause) | Free lab and Act I; Premium for the full course |
No sign-up is needed to start: open the lab and place your first transistor, or read the free theory course. The account (and the AI tutor) are optional.
More comparisons: Logic simulators
See for yourself: build a logic gate from transistors in the simulator, then follow the path from sand to an 8-bit CPU.
Open the digiwleea lab →Frequently asked
What is CircuitSim?
CircuitSim is a free digital logic circuit simulator by Roi Atalla, written in Java as a replacement for Logisim. It has gates, subcircuits, a clock, RAM, ROM, a transistor and a 7-segment display among its built-in components.
How do I download CircuitSim?
From its website, ra4king.github.io/CircuitSim, or the GitHub releases page. It needs Java 8 or later; the site recommends Java 8u152 and lists 8u40 as the minimum.
Can I run CircuitSim in a browser?
No, CircuitSim is a desktop Java application. Browser logic simulators include digiwleea and CircuitVerse; our Logisim online page lists more.
Is CircuitSim the same as Logisim?
No. It is a separate program written by Roi Atalla because of problems he found with Logisim, so it has its own file format and interface, though the way you wire circuits is similar.