An explanation on how mac addresses are derived on the ESP32:

https://docs.espressif.com/projects/esp … dress.html

An explanation for how many universal (unique) mac addresses are allocated to each ESP32

https://docs.espressif.com/projects/esp … ystem.html

Read MAC Address

8 bytes are stroed in total. 6 bytes for MAC-48, 8 bytes for EUI-64

#include "esp_mac.h"

//**********************************************************
//**********************************************************
//********** READ THIS DEVICES UNIQUE MAC ADDRESS **********
//**********************************************************
//**********************************************************
//MacAddress
//	8 byte array. (6 bytes for MAC-48, 8 bytes for EUI-64)
//Returns:
//	1 = success
//	0 = failed
int ReadFactorySetMacAddress (uint8_t *MacAddress)
{
	if (esp_efuse_mac_get_default(MacAddress) != ESP_OK)
	{
		return(1);
	}
	else
	{
		MacAddress[0] = 0;
		MacAddress[1] = 0;
		MacAddress[2] = 0;
		MacAddress[3] = 0;
		MacAddress[4] = 0;
		MacAddress[5] = 0;
		MacAddress[6] = 0;
		MacAddress[7] = 0;
		return(0);
	}
}

Display device MAC address to console

#include "esp_mac.h"

	uint8_t MacAddress[8];
	if (esp_efuse_mac_get_default(MacAddress) != ESP_OK)
		ESP_LOGI(TAG, "Unable to read MAC address");
	else
		ESP_LOGI(TAG, "MAC address: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X", (uint16_t)MacAddress[0], (uint16_t)MacAddress[1], (uint16_t)MacAddress[2], (uint16_t)MacAddress[3], (uint16_t)MacAddress[4], (uint16_t)MacAddress[5], (uint16_t)MacAddress[6], (uint16_t)MacAddress[7]);