Mongoose OS is now officially recommended by Espressif Systems as a firmware toolkit for ESP8266 and ESP32:

Mongoose OS is an open source Operating System for the Internet of Things:

  • It reduces time and costs of firmware development by up to 90%,
  • Provides reliable, ready to go infrastructure for commercial products,
  • Has high security standards, including flash encryption and external crypto chips support.

Using Mongoose OS developers can code firmware either in C or JavaScript and seamlessly connects products to the preferred IoT Cloud.