This document provides an introduction and overview of WebUSB, including: - A brief history of efforts to connect USB devices to web browsers before WebUSB. - An explanation that WebUSB allows USB devices to be accessed safely from web applications using a familiar API, in a cross-platform way. - An overview of the WebUSB specification and how developers can use it to build JavaScript libraries for USB devices that work across browsers. - A demonstration of how WebUSB can be used to connect hardware like microcontrollers and display screens to web applications.