Free Online Arduino Simulator
Run Sketches in Your Browser
Write Arduino code and simulate it instantly — real AVR8 emulation at 16 MHz with 48+ interactive electronic components. No install, no cloud, no account required.
Free & open-source · No signup required · Runs 100% in your browser
What can you simulate?
Velxio simulates Arduino programs with full AVR8 CPU accuracy — including GPIO ports, hardware timers, USART, ADC, PWM, SPI, and I2C. No approximations, no shortcuts.
Arduino Uno & Nano
Full ATmega328P simulation at 16 MHz. PORTB, PORTC, PORTD register emulation. All 14 digital and 6 analog pins.
Arduino Mega 2560
ATmega2560 with 256 KB flash, 54 digital pins, 16 analog inputs, and 4 hardware USART channels.
48+ Electronic Components
LEDs, resistors, buttons, buzzer, servo, ultrasonic sensor, ILI9341 TFT, 16×2 LCD, NeoPixel, DHT22, and more.
Serial Monitor
Real-time TX/RX with auto baud-rate detection. Send commands and view Serial.print() output live.
Multi-file Sketches
Write .ino, .h, and .cpp files in a VS Code-style Monaco editor — full multi-file Arduino project support.
Library Manager
Search and install any library from the full Arduino library index directly inside the simulator.
How the simulator works
Velxio uses avr8js — the battle-tested open-source AVR8 emulation library — to execute your compiled firmware byte-for-byte, exactly as it would run on physical hardware.
1. Write
Write your Arduino sketch in the Monaco editor with C++ syntax highlighting and autocomplete.
2. Compile
Click Compile. arduino-cli produces a real .hex file — the same output as the Arduino IDE.
3. Simulate
The .hex is loaded into the AVR8 emulator. Your program executes at 16 MHz and drives the visual components.
Frequently Asked Questions
- Is this Arduino simulator free?
- Yes. Velxio is completely free and open-source (GNU AGPLv3). No account, no payment, no cloud subscription — run it in your browser or self-host it with one Docker command.
- Does the Arduino simulator work without installing anything?
- The simulation engine runs entirely in your browser. Compiling code requires the arduino-cli backend, which you can run locally or via Docker. No IDE installation is needed.
- What Arduino boards can I simulate?
- Velxio supports 19 boards: Arduino Uno (ATmega328P), Arduino Nano, Arduino Mega 2560, ATtiny85, Arduino Leonardo, Arduino Pro Mini (AVR8) — plus Raspberry Pi Pico (RP2040), ESP32-C3 / XIAO ESP32-C3 / CH32V003 (RISC-V), ESP32 / ESP32-S3 / ESP32-CAM (Xtensa via QEMU), and Raspberry Pi 3B (Linux via QEMU).
- Can I simulate LEDs, sensors, and displays?
- Yes. Velxio includes 48+ interactive wokwi-elements: LEDs, resistors, buttons, servo motors, ultrasonic sensors, ILI9341 TFT displays, LCD, NeoPixel strips, buzzers, DHT22, and more.
- Is Velxio a Wokwi alternative?
- Yes. Velxio is a free, self-hosted alternative to Wokwi. It uses the same avr8js emulation library and wokwi-elements visual components, but runs entirely on your own machine with no cloud dependency.
Ready to simulate your Arduino?
Open the editor and start coding in seconds — no setup, no install, no account needed.
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