Free, and it runs in your browser
Plug real components into a breadboard in realistic 3D, wire them up, program an Arduino, a Pico or an FPGA, and watch it all behave exactly like it would on your desk.
Simulated, not animated
That glow isn't a special effect. A real circuit solver works out the current through the LED, live, and the light follows.
So when you break the circuit
Pull a leg out of the board and the current stops. It goes dark, just like the real thing would.
Every part is real.
Every result is earned.
Live simulation
Change a value while the circuit is running and it responds straight away, so you see cause and effect instead of just an answer. Try it on the LED.
Pop. That's the magic smoke. A real LED wouldn't come back from this one.
Drag towards 47 Ω to see what too much current does.
Under the hood
Every circuit is solved by ngspice, the open-source SPICE simulator used to design real hardware. It's compiled to WebAssembly and runs on your own device, so there's nothing to install and nothing to wait for.
Clip up to four probes onto any holes and watch the voltages over time. Here's a 555 timer: its capacitor charging and discharging, and the square wave it makes.
Logic chips run on SPICE's own digital models right alongside your transistors and capacitors. Mix a 555, some gates and a counter on one board.
Wire an LED straight across a battery or put a capacitor in backwards. You'll see it fail, smoke and all, and learn why without buying a single spare.
Arduino and Pico, built in
Drop an Arduino Nano or a Raspberry Pi Pico on the board and write your code right beside it. The simulated chip runs every instruction against your circuit, all inside your browser. No IDE, no USB cable, no drivers.
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup() {
lcd.begin(16, 2);
lcd.print("Hello, world!");
}
void loop() {
lcd.setCursor(0, 1);
lcd.print("Uptime: ");
lcd.print(millis() / 1000);
lcd.print(" s");
}Uploaded. The program uses 2,476 of 30,720 bytes of flash.
The same avr-gcc the Arduino IDE uses, built for the web. Your sketch compiles on your own device, and mistakes point straight at the line.
ServoLiquidCrystalWireSPIEEPROMSoftwareSerialAdafruit SSD1306Adafruit GFXDHTBMP280LedControl
Everything your program prints shows up beside it, and you can type back. Sensors have panels, so you can set the temperature or move the object in front of the sonar.
Click next to a line and the whole bench freezes when the chip gets there, voltages and all. Step on and watch what changes.
The Pico runs the real MicroPython firmware on an emulated RP2040. Write main.py beside it, press Upload and it starts at once, with nothing to compile. Read the ADCs, fade LEDs with PWM, draw on an OLED over I²C and type back through the serial monitor.
from machine import ADC, Pin
import time
sensor = ADC(4)
led = Pin("LED", Pin.OUT)
while True:
volts = sensor.read_u16() * 3.3 / 65535
celsius = 27 - (volts - 0.706) / 0.001721
led.toggle()
print("{:.1f} °C".format(celsius))
time.sleep(1)FPGA, built in
Put a UPduino v3.1 on the board and design your own hardware for its iCE40 FPGA. Yosys turns your Verilog into logic right in the browser, and the simulator runs it on the board's real pins, wired to whatever you've built around it.
Synthesised.
The open-source synthesis tool behind real iCE40 projects, built for the web. It downloads once, then works offline like everything else.
SB_HFOSCSB_LFOSCSB_PLL40_CORESB_IOSB_RGBA_DRV
Split a design across as many .v files as you like, and assign pins in a .pcf, just like the real toolchain.
Synthesis errors and warnings land on the line of Verilog they came from, in whichever file it's in.
The parts drawer
From your very first resistor to sensors, displays, motors and hundreds of real chips by their part numbers. Drag one out and it snaps into the board.
Phone, tablet, laptop
Built for touch from the start. Swipe through the parts drawer, drag a part onto the board, pinch to look closer and tap a button to press it. The same circuit works on every screen you own.
For everyone who's curious
Build it, break it, fix it. Tap any part to see what it does and read its live voltage and current, so the numbers in your textbook finally mean something.
Build a circuit once and share it as a link. Every student opens the same thing on whatever device the school has, and nobody has to hunt for a missing jumper wire.
Try an idea before you order parts. Check that resistor value, see if the 555 really blinks at 1 Hz, and only then warm up the soldering iron.
A few of the 32 ready-made examples
Questions
Yes. There's no trial, no account and nothing to unlock. Open it and build.
No. It runs in any modern browser on Windows, macOS, Linux, ChromeOS, iOS and Android, and keeps working offline after your first visit. If you like, you can add it to your home screen or dock so it opens like an app.
Circuits are solved with ngspice, a full SPICE simulator, using models of real parts like the 2N3904 transistor and the NE555 timer. It's the same kind of maths used to design real electronics, so what you see is what the circuit would do.
Your work is kept in your browser between visits. You can also save a circuit to a file, or share it as a link that contains the entire circuit.
The Arduino Nano, with its ATmega328P, the same chip as the Uno. Write a sketch in the built-in editor and upload it, or load a .hex you exported from the Arduino IDE. Popular libraries for servos, LCDs, OLED displays and sensors are included.
And the Raspberry Pi Pico, which runs MicroPython. Write your program in the editor or load a .py file, and it runs as main.py, just like on the real board. The OLED driver is built in.
And the UPduino v3.1, with a Lattice iCE40UP5K FPGA. Write Verilog, set its pins in a .pcf, and it's synthesised with Yosys in your browser, then simulated with the rest of your circuit.
Free, in your browser, on any device. Plug something in.
Open Breadboard Simulator