arduino-esp32/libraries/ESP32/examples/ChipID/GetChipID/GetChipID.ino

uint64_t chipid;  

void setup() {
	Serial.begin(115200);
}

void loop() {
	chipid=ESP.getEfuseMac();//The chip ID is essentially its MAC address(length: 6 bytes).
	Serial.printf("ESP32 Chip ID = %04X",(uint16_t)(chipid>>32));//print High 2 bytes
	Serial.printf("%08X\n",(uint32_t)chipid);//print Low 4bytes.

	Serial.printf("ESP32 Chip model = %s Rev %d\n", ESP.getChipModel(), ESP.getChipRevision());
	Serial.printf("This chip has %d cores\n", ESP.getChipCores());

	delay(3000);

}