The Serial API provides an interface for connecting to serial devices, either through a serial port on the user’s system or removable USB and Bluetooth devices that emulate a serial port. This API has been requested by the hardware developer community, especially developers building educational tools, as a companion to the WebUSB API because operating systems require applications to communicate with USB-based serial ports using their higher-level serial API rather than the low-level USB API.
Users, especially in the educational, hobbyist and industrial sectors, connect peripheral devices to their computers that require custom software to control. For example, robotics are often used to teach computer programming and electronics in schools. This requires software which can upload code to a robot and/or control it remotely. In an industrial or hobbyist setting a piece of equipment such as a mill, laser cutter or 3D printer is controlled by a program running on a connected computer. These devices are often controlled by small microcontrollers via a serial connection.
Docs: https://web.dev/serial/
Samples: https://googlechromelabs.github.io/serial-terminal
Explainers: https://github.com/WICG/serial/blob/gh-pages/EXPLAINER.md