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
Datacopia is designed for ease of use and quick implementation, making it suitable for non-technical users, while D3.js offers extensive customization and flexibility for developers, albeit with a steeper learning curve. Datacopia is best for straightforward data visualization projects, whereas D3.js excels in complex, interactive visualizations.