The Arduino UNO R4 WiFi has the same size and pin layout as the classic Uno, but is a much more powerful board. Its main processor is a 48 MHz 32-bit Renesas RA4M1 (256 KB flash, 32 KB RAM), and the on-board ESP32-S3 module adds Wi-Fi and Bluetooth (BLE). On the front there is a 12x8 red LED matrix you can draw on from code, plus a USB-C port, a 12-bit DAC (A0), a real-time clock (RTC), a CAN bus and a Qwiic connector. Its pins run at 5 V, so most shields and modules written for the Uno plug straight in. Wi-Fi uses the WiFiS3 library and the matrix uses Arduino_LED_Matrix. Most Uno R3 sketches run as they are; old code that touches AVR registers directly (for example Timer1 libraries) has to be changed. It suits web servers, internet clocks, weather displays and IoT projects.