Over The Air (OTA)
Over-the-Air (OTA) is a method of delivering firmware or software updates to a device wirelessly, without requiring a physical connection. The device receives the update over a radio link — typically WiFi — downloads the new firmware, and applies it. OTA updates are standard practice for embedded devices and IoT hardware because they allow updates to be deployed remotely at scale, without physically accessing each unit.
The alternative to OTA is flashing the device by connecting it directly to a computer via USB or a serial interface. This is typically required only for the initial firmware install, after which OTA can take over for subsequent updates.
In This Home
ESPHome-programmed microcontrollers in the home are almost all updated OTA over WiFi. The exception is devices that spend most of their time in deep sleep to conserve battery power — these cannot maintain a WiFi connection and must be flashed directly when their firmware needs updating.