Mokxi is a free electronics and microcontroller simulator that runs in your web browser. This is its editor: a breadboard, the parts bin and a code editor in one tab. Wire a circuit, write the sketch in C++ for an Arduino, ESP32, Raspberry Pi Pico or STM32 board, and press Run: it compiles in the browser and runs with the circuit, on your own computer. No install and no account needed.
The editor needs JavaScript and WebAssembly. Turn JavaScript on and reload, or read about it first: