iCircuit alternative: digital logic in the browser, free to start
iCircuit is a real-time circuit simulator app for iPhone, iPad, Mac, Windows and Android. Its site describes designing "analog and digital circuits from more than 300 components", measuring them with a built-in multimeter and oscilloscope, and programming the microcontrollers in them, with everything simulating live: there is no run button, wires glow with their voltage and moving dots show the current. Its parts include passives, transistors and op-amps, gates, flip-flops, counters and 4000- and 7400-series logic ICs, and it runs Arduino and ESP32 sketches, PIC code and, since version 1.16 (on iPhone, iPad and Mac), MicroPython on an emulated Raspberry Pi Pico, SPICE subcircuits and Verilog or VHDL. If what you want is to understand digital logic and how a CPU works, digiwleea is a narrower, deeper tool that runs in any browser.
What iCircuit is good at
Breadth and immediacy. One app covers Ohm's law, transients, transistors, logic and microcontrollers, with an oscilloscope (including FFT, Bode and XY views), a multimeter and live gauges, and it warns about over-voltage and over-power instead of letting a part burn out. It runs natively on phones and tablets as well as computers, and its site says it is a one-time purchase with free updates (prices vary by store), with an optional iCircuit Pro subscription on iPhone, iPad and Mac. (digiwleea is an independent project, not affiliated with iCircuit or its developer.)
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, capacitors or microcontrollers. In exchange it goes deep where iCircuit gives you ready-made parts: you build the gates themselves from CMOS transistors, then adders, latches, registers, RAM and an 8-bit CPU that you program in assembly, with every part checked against its truth table, a guided 40+ level course and an AI tutor (Wleea). It runs in the browser with nothing to install, and the lab and the first act are free. For analog electronics and microcontroller projects, iCircuit is the better fit; to learn how logic becomes a computer, digiwleea is.
| iCircuit | digiwleea | |
|---|---|---|
| Runs on | Apps for iPhone, iPad, Mac, Windows and Android | Any modern browser, nothing to install |
| Simulates | Analog and digital circuits live, with voltages and currents | Digital logic at the switch level: 0, 1 and floating |
| Parts | More than 300, from resistors to microcontrollers | Transistors, and the gates, flip-flops and memory you build from them |
| Learning path | Built-in example circuits | A 40+ level course from transistor to CPU |
| Price | One-time purchase (varies by store); optional Pro subscription on Apple devices | 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 iCircuit free?
No. Its site describes it as a one-time purchase with free updates, priced by each app store, plus an optional iCircuit Pro subscription on iPhone, iPad and Mac. digiwleea's lab and first act are free in the browser.
Does iCircuit simulate logic gates?
Yes. Alongside its analog parts it has gates, flip-flops, counters, 555 timers and 4000- and 7400-series logic ICs, and from version 1.16 an HDL element for Verilog and VHDL on iPhone, iPad and Mac.
Is there a free online alternative to iCircuit?
For analog circuits in the browser, Falstad's circuit simulator is free (see our Falstad comparison). For digital logic from transistors up to a CPU, digiwleea runs in the browser and its lab and first act are free.
Can I build a CPU in iCircuit?
You can wire logic ICs and program microcontrollers in it. digiwleea is built around that path instead: its course has you make every part of an 8-bit CPU yourself, checked as you go, and then program it in assembly.