Like DigitalJS, but you build the circuit by hand
DigitalJS is a free, open-source (BSD-2-Clause) digital circuit simulator written in JavaScript by Marek Materzok. It is designed to simulate circuits synthesized by hardware design tools like Yosys, and its online version turns Verilog and SystemVerilog code into an interactive circuit diagram in the browser. If that is what brought you here, digiwleea is a free, in-browser alternative with a different angle: you build a computer from the transistor up.
What DigitalJS is good at
If you are learning Verilog, DigitalJS is excellent: you write HDL, and it shows you the actual hardware that code becomes, with inputs you can toggle and signals you can follow. It was built as a teaching tool, and readability of the generated diagrams is one of its stated priorities.
How digiwleea is different
digiwleea works the other way round. Instead of writing code and looking at the circuit it produces, you place every part and wire yourself, starting from individual CMOS transistors, and the simulator checks each gate against its truth table as you go. A guided 40+ level course takes you from one transistor through adders, latches, registers and RAM to a working 8-bit CPU, with an AI tutor (Wleea) to explain faults. When you are ready for HDL, the free Verilog lessons describe the same circuits in code. The two pair well: build it by hand here, then write it in Verilog and watch DigitalJS draw it.
| DigitalJS | digiwleea | |
|---|---|---|
| How you make a circuit | Write Verilog, synthesize, view | Place parts and wires by hand |
| Smallest building block | Synthesized gates and cells | CMOS transistors (build the gates too) |
| Guided course to a CPU | No (a simulator) | Yes, 40+ levels |
| HDL | Verilog / SystemVerilog input | Verilog and VHDL theory lessons |
| AI tutor | No | Yes (Wleea) |
| Price | Free, open source | 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.
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
Is digiwleea a good DigitalJS alternative?
Yes, if you want to understand digital logic from the ground up. digiwleea is a free, in-browser simulator with a guided 40+ level course where you build every gate from CMOS transistors and work up to a real 8-bit CPU, with an AI tutor to help.
Is digiwleea free?
The sandbox lab and the first act of the course are free and need no sign-up. An optional account adds the AI tutor and cross-device sync; the full course and expanded AI tutoring are included in the monthly or annual Premium subscription.
Do I need to install anything?
No. digiwleea runs entirely in your browser, on desktop or mobile, and works offline once loaded.