Chart.js is an open-source charting library for JavaScript application developers, currently the most popular one according to GitHub stars and npm downloads. It's a feature-rich and well-supported library that provides a set of frequently used chart types, plugins, and customization options. Chart.js has built-in TypeScript typings and compatibility with all popular JavaScript frameworks, including React, Vue, Svelte, and Angular. The library is actively developed and maintained by the community, with minor releases on an approximately bi-monthly basis and major releases with breaking changes every couple of years. The v4 release contains limited breaking changes and primarily focuses on bug fixes as well as quality of life and developer experience improvements. Chart.js supports tree-shaking, allowing developers to remove unused code from the JavaScript bundle, resulting in a smaller bundle size. It also has an extensive API for customization and plugin development.