Mokxi and Qucs-S, compared fairly
Mokxi is a free, browser-based alternative to Qucs-S for SPICE work on machines that cannot install a desktop simulator. It runs SPICE decks on an engine checked against ngspice and runs breadboard circuits live, without Qucs-S’s choice of engines or its RF analyses. Qucs-S is a free, open-source circuit simulation program with a Qt interface over several engines: ngspice, Xyce, SpiceOpus, and Qucsator for RF work. It runs on Linux, Windows, macOS and FreeBSD. Mokxi is a free circuit and firmware simulator in a browser tab that runs SPICE decks on its own engine. Here is where each one is the right answer.
Last checked September 2026
- 228parts on the bench
- 31boards running now
- 1.00xreal time, on every board
The Mokxi editor running an RL filter on the bench, with a signal generator driving it and a two-channel oscilloscope on both ends.
Where Qucs-S leads
These are the strongest reasons to choose Qucs-S today.
- Free and open source under the GPL-2.0, a desktop program that works offline on Linux, Windows, macOS and FreeBSD.
- A choice of engines: ngspice, which reads most industrial SPICE models, Xyce, SpiceOpus, and Qucsator for RF and microwave circuits.
- Analyses Mokxi does not have, among them S-parameters, harmonic balance, distortion, pole-zero, sensitivity and spectrum analysis.
- Schematic capture tied to all of those engines, so one drawing can be run on whichever suits the job.
Where Mokxi leads
These are working parts of Mokxi you can open and test for yourself.
- Runs in a browser tab with nothing to install, including on a school Chromebook.
- SPICE decks run in the editor: .op, .tran, .ac, .dc, .tf, .noise and .meas with subcircuits, parameters and model cards, on an engine checked against ngspice on 42 benchmark circuits.
- A breadboard with bench instruments wired in as parts: a signal generator, a two-channel oscilloscope, a multimeter and a bench supply.
- Microcontrollers on the same canvas: 31 boards running compiled C++, so a circuit and the code that drives it are tested together.
Side by side
Last checked September 2026. If anything here has gone stale, that is our mistake and we want to know.
| Mokxi | Qucs-S | |
|---|---|---|
| Aimed at | Breadboard circuits, instruments and firmware | Analog and RF circuit simulation |
| Runs in | A browser tab, including on Chromebooks | A Linux, Windows, macOS or FreeBSD install |
| Price | Free; paid plans for classes and more room | Free and open source |
| Engines | Its own SPICE engine, checked against ngspice | ngspice, Xyce, SpiceOpus or Qucsator |
| Analyses | Operating point, transient, AC, DC sweeps, transfer function, noise and .meas | AC, DC, transient, noise, distortion, pole-zero, S-parameters, harmonic balance and more |
| Open source | No | Yes |
Which one should you use
Straight answers. Where the other one is the right call, we say so.
You design RF or microwave circuits
Qucs-S, with Qucsator. Mokxi has no RF analyses.
You need a particular engine such as Xyce, or models only ngspice reads
Qucs-S.
Your class works on Chromebooks
Mokxi runs there with nothing to install.
You want a circuit and the microcontroller driving it tested together
Mokxi.
Compare the other options
The same straight comparison for the tools teachers, students and makers also consider.
In short
Should I use Mokxi if you design rf or microwave circuits?
Qucs-S, with Qucsator. Mokxi has no RF analyses.
Should I use Mokxi if you need a particular engine such as xyce, or models only ngspice reads?
Qucs-S.
Should I use Mokxi if your class works on chromebooks?
Mokxi runs there with nothing to install.
Should I use Mokxi if you want a circuit and the microcontroller driving it tested together?
Mokxi.
Try it yourself
A comparison page is somebody else’s opinion. Open the editor, press Run and make up your own mind.
Free forever. Every board and part. Saves your projects. Works on Chromebooks.