D3.js, available at https://d3js.org, is a powerful JavaScript library used for creating dynamic, interactive data visualizations in web browsers. It enables developers to manipulate documents based on data using HTML, SVG, and CSS. By leveraging modern web standards, D3.js facilitates the creation of complex visual representations without relying on proprietary frameworks. Its flexibility and granularity make it a popular choice for developers looking to build customized data-driven interfaces and visualize data with precision and control.