D3.js (D3 for Data-Driven Documents) is a JavaScript library for producing dynamic, interactive data visualizations in web browsers. Developed by Mike Bostock
License: Open Source
D3.js is a powerful and flexible library for creating complex and highly customizable visualizations, but it comes with a steep learning curve. Plotly, on the other hand, is more user-friendly and offers a variety of built-in chart types, making it easier for beginners to create interactive visualizations quickly.