The free open source firmware for ESP82XX / ESP32 chip based devices. The firmware was created by Theo Arendst and is constantly updated.
It all started on January 25, 2016 as Sonoff-MQTT-OTA. Theo Arendst's goal was to provide ESP8266-based ITEAD Sonoff devices with MQTT and 'over the air' or OTA firmware.
What started as a simple way to hack a cloud-connected Sonoff Basic (one of the first affordableand accessible smart home devices on the market) into a locally controlled device has evolved into a full-fledged ecosystem for virtually any ESP82XX / ESP32-based device.
If you're not willing to tinker and learn...
THEN YOU DON'T NEED TO READ ANY FURTHER!
Tasmota is not a commercial product and support is limited. You must be prepared to identify and solve potential problems yourself.
The Tasmota firmware program is licensed under GPL-3.0