KiCad simulator alternative: digital logic in your browser
KiCad is a free, open-source, cross-platform suite for schematic capture and PCB design, and its Schematic Editor includes circuit simulation using ngspice. According to the KiCad 10 manual, you draw a schematic with parts that have SPICE models (a Simulation_SPICE symbol library comes with KiCad), choose an analysis, and view the results in a plot window: DC operating point, DC sweep, AC small-signal, transient, pole-zero, noise, S-parameter and FFT analyses, or a custom SPICE command. The same schematic then carries on to PCB layout. If what you want is to learn digital logic rather than verify a board's analog behavior, digiwleea is a free browser alternative built for that.
What KiCad's simulator is good at
Checking a real board design without leaving it: the schematic you simulate is the one you lay out, so filters, power supplies and amplifier stages can be tested with real device models before ordering a PCB. Because it is ngspice underneath, it handles analog and mixed-signal circuits with the full range of SPICE analyses. (digiwleea is an independent project, not affiliated with KiCad.)
How digiwleea is different
digiwleea simulates digital logic only, at the switch level: every wire is 0, 1 or floating, and there are no voltages, currents or device models. In exchange it is immediate: you build NOT and NAND from CMOS transistors in the browser and watch every wire change as you click, then work up to adders, latches, registers, RAM and an 8-bit CPU through a 40+ level course where every part is checked against its truth table, with an AI tutor (Wleea). For SPICE work outside KiCad, see our ngspice and LTspice comparisons.
| KiCad's simulator | digiwleea | |
|---|---|---|
| Runs on | Windows, macOS and Linux (desktop suite) | Any modern browser, nothing to install |
| Simulates | Analog and mixed-signal circuits with ngspice: OP, DC, AC, transient, noise and more | Digital logic at the switch level: 0, 1 and floating |
| Results | Plots and annotated node voltages | Live wire values, truth tables and timelines |
| Also does | Schematic capture and PCB layout | A 40+ level course from transistor to CPU |
| Price | Free and 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.
More comparisons: Electronics and SPICE 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
Can I use KiCad online?
KiCad is a desktop suite for Windows, macOS and Linux, so it is installed rather than run in a browser. For digital logic in the browser, digiwleea needs no install.
Does KiCad have a simulator?
Yes. KiCad's Schematic Editor includes circuit simulation using ngspice, with operating point, DC sweep, AC, transient, pole-zero, noise, S-parameter and FFT analyses, and custom SPICE commands.
Can KiCad simulate logic gates?
Through ngspice it can simulate circuits with SPICE models, including digital parts that have models. For learning digital logic interactively, a logic simulator such as digiwleea shows every gate's output live as you click the inputs.
Is there an online alternative to KiCad's simulator?
For digital logic, digiwleea runs in the browser with a free lab and first course act. For analog circuits online, Falstad's circuit simulator is free in the browser.