React

React is a declarative, component-based JavaScript library for building user interfaces, maintained by Meta and a large open source community. It introduced the virtual DOM to minimize expensive real DOM updates, and popularized composing UIs from small, reusable components.

React’s unidirectional data flow and hooks API make it straightforward to manage state and side effects within components. It is widely used for single-page applications and can be rendered on the server via frameworks such as Next.js.