Online Arduino/AVR MCU Simulator
Run real ATmega328P firmware (the core of Arduino Uno) in your browser: six hands-on examples — blink, knight-rider, serial, pushbutton input, PWM breathing LED and traffic light. Open the code editor, change the C, and cloud-compile it straight into the simulator. No install required; then source the MCU, dev board and parts in one click.
How is this different from Tinkercad?
The core is avr8js (MIT, also the AVR engine behind Wokwi), the editor is CodeMirror (MIT), and the cloud compiler is a sandboxed GCC-AVR — all legally self-hosted for commercial use. You can edit the C code, compile it into the simulator, wire inputs, watch PWM and UART, then jump straight into a 15M-part live inventory: learn, code, buy, BOM and prototype in one place.