Arduino Simulator Online

Write a sketch, press Run and watch the circuit work. A simulated Uno in your browser, nothing to install.

Example circuits

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
}

Run Arduino code without a board

Pick a circuit, write the sketch and press Run. The LED blinks, the servo turns when you drag the knob, the LCD prints your text and the serial monitor shows every Serial.println. Nothing to install and no account needed.

Your sketch is compiled with Arduino's own toolchain for an Uno and runs on a simulated ATmega328P, the chip on the board, instruction by instruction. So delay(), millis(), analogWrite() and the timers behave the way they do on real hardware, and a sketch that works here is ordinary Arduino code you can upload to a board.

What makes this Arduino simulator useful

Eleven ready circuits: LEDs, an RGB LED, a pushbutton, a potentiometer, a light sensor, a buzzer, a servo, a 7-segment display, a 16x2 LCD, a NeoPixel ring, an ultrasonic distance sensor and a thermistor, already wired to the Uno.
Use the parts while the sketch runs: press the button, turn the knob, move the light or the distance slider, and watch your code answer.
A serial monitor that reads and sends, and a Signals view that draws every wired pin over time, so you can see a PWM wave or a button bounce.
The libraries beginners reach for: Servo, LiquidCrystal, LiquidCrystal_I2C, Adafruit_NeoPixel, Wire, SPI, EEPROM and SoftwareSerial. Compiler errors read the way the Arduino IDE prints them.

What you can try in the Arduino simulator

Blink: change the two delay() values and see the LED follow. Then blink it without delay(), using millis().
Servo and knob: map the potentiometer's analogRead() to an angle with map() and drive the servo with it.
Distance sensor: time the echo of an HC-SR04 with pulseIn(), turn it into centimeters and print it on the serial monitor.

Arduino simulator FAQ

Do I need an Arduino board to use this?

No. The board is simulated in your browser, so you can write and test sketches on any computer, a Chromebook or a phone. When you do get a board, the same sketch uploads to it from the Arduino IDE.

Can I build my own circuit?

Not yet. You pick one of the eleven circuits above and write any sketch you like for it. Each circuit lists its parts and pins on the board, so you know which pin the LED, the button or the sensor is on.

How close is it to a real Uno?

Very close for what a beginner writes. The sketch is compiled by the same compiler the Arduino IDE uses and runs on a simulation of the Uno's chip, so timing, PWM and serial behave as on the board. The parts are models: a button bounces in a fixed pattern, and the sensors give exactly the value you set with their slider.

Is it free, and is my code saved?

It is free and needs no account. Your edits to each example are kept in this browser, so you can close the tab and come back. Reset puts the current example back the way it started.

Is this made by Arduino?

No. Coddy is not affiliated with Arduino. The simulator is Coddy's own and runs an Uno-compatible board.

How do I learn Arduino programming?

Start with the examples here: change one number, press Run and see what happens. When you want a path, Coddy's Arduino course goes from a first blink to buttons, sensors, displays and six projects, one short lesson at a time, on the same simulated board you see on this page.