Mokxi and Falstad’s circuit simulator, compared fairly
Paul Falstad’s circuit simulator, often called CircuitJS, is a free, open-source, browser-based tool for real-time analog and digital circuit simulation with live current and voltage animation. It is built to teach how a circuit behaves, and its main simulator does not run Arduino firmware. Mokxi runs real firmware on a real breadboard. The two are complementary rather than competing on the same job.
Last checked September 2026
- 505parts on the bench
- 45boards running now
- 1.00xreal time, on every board
The Mokxi editor running a 555 astable on the bench, with an oscilloscope showing the square wave and a meter reading its average.
Where Falstad (CircuitJS) leads
These are the strongest reasons to choose Falstad (CircuitJS) today.
- Free, open source, and has run in a browser for a very long time, with a huge library of shared, linkable example circuits.
- Excellent live animation of current flow and voltage, which makes it a genuinely strong tool for building intuition about analog and simple digital circuits.
- No account, no boards to pick, and a circuit is shareable as a single link with its state encoded in the URL.
- Standalone offline builds for Windows, macOS and Linux, and a separate AVR8js demo page that runs a small Arduino sketch against a circuit.
Where Mokxi leads
These are working parts of Mokxi you can open and test for yourself.
- Runs real, compiled C++ on 42 boards, from the Arduino Uno to ESP32, Pico and STM32 boards, as the heart of the tool rather than a demo.
- A breadboard at real 0.1 inch pitch, wired the way a physical build is wired, rather than a schematic-style canvas.
- Real parts, including a 74HC595 shift register, an NE555 and 74HC-series logic, alongside a microcontroller on the same board.
- SPICE decks run in the editor, on an engine checked against ngspice, and bench instruments are parts you wire in.
Side by side
Last checked September 2026. If anything here has gone stale, that is our mistake and we want to know.
| Mokxi | Falstad (CircuitJS) | |
|---|---|---|
| Aimed at | Firmware and breadboard work | General circuit theory and analog intuition |
| Runs firmware | Yes, real compiled C++ on 42 boards | Not in the main simulator; a separate AVR8js demo runs Arduino sketches |
| Layout | A real breadboard | A schematic canvas |
| Offline | Keeps running once the tab is open | Standalone builds for Windows, macOS and Linux |
| Sharing | A link that carries the whole circuit, no account needed, or a saved project’s link | State encoded directly in the URL |
| Price | Free; paid plans for classes and more room | Free |
Sources for Falstad (CircuitJS)
Which one should you use
Straight answers. Where the other one is the right call, we say so.
You want to build intuition about a generic RLC or diode circuit
Falstad’s simulator is built exactly for that.
You want to run an actual Arduino, ESP32 or Pico sketch
Mokxi. Falstad’s main simulator does not run firmware, and its AVR8js page is a demo.
You want to wire a project on something that looks like a real breadboard
Mokxi.
You want to share a tiny circuit as a single link with no account
Either. Both put the whole circuit in the link, so neither needs an account.
Import your Falstad circuit
Paste a CircuitJS link, the kind File, Export As Link makes, or the text from Export As Text, into Mokxi’s import page. The circuit is stored in the link itself, so Mokxi reads it there and fetches nothing. Resistors, capacitors, inductors, sources, diodes, LEDs, transistors, MOSFETs, op-amps, pots, switches, the 555 and logic gates become Mokxi parts on the same nets.
A CircuitJS op-amp is powered without wires, so the import gives it a supply; CircuitJS needs no ground symbol and Mokxi does, so the report asks for one when the circuit had none. Elements Mokxi does not have, such as transformers and transmission lines, become labeled notes.
Compare the other options
The same straight comparison for the tools teachers, students and makers also consider.
In short
Can I import a Falstad CircuitJS circuit?
Yes. Paste its link or its Export As Text on the import page. The analog parts Mokxi has come across on the same nets, and anything else is named in the report and left as a note.
Should I use Mokxi if you want to build intuition about a generic rlc or diode circuit?
Falstad’s simulator is built exactly for that.
Should I use Mokxi if you want to run an actual arduino, esp32 or pico sketch?
Mokxi. Falstad’s main simulator does not run firmware, and its AVR8js page is a demo.
Should I use Mokxi if you want to wire a project on something that looks like a real breadboard?
Mokxi.
Should I use Mokxi if you want to share a tiny circuit as a single link with no account?
Either. Both put the whole circuit in the link, so neither needs an account.
Try it yourself
A comparison page is somebody else’s opinion. Open the editor, press Run and make up your own mind.