React

JavaScript library for building user interfaces from reusable components. Lets you compose UIs from small pieces like Thumbnail, LikeButton, and Video, then combine them into screens and full applications. Uses a declarative style where components receive data and return what should appear, with React updating the screen when data changes.

Maintained by Meta and used across thousands of components at scale. Over 100,000 components at Meta help validate every change on surfaces with over a billion users. React differentiates from alternatives by staying a library rather than a framework: it handles rendering and state updates but leaves routing and data fetching to companion tools like Next.js and React Router. The React Foundation, hosted by the Linux Foundation, stewards the project. Millions of developers visit the documentation monthly.

Key capabilities:

• Component-based architecture with JSX for markup colocated with rendering logic
• Hooks for local state, effects, and reusable behavior without class components
• Virtual DOM reconciliation for efficient updates when data changes
• Server Components and streaming HTML for full-stack apps via frameworks
• React Native and Expo for native mobile apps using the same skills as web

Teams use React for SPAs, dashboards, e-commerce, content sites, and internal tools. Developers add interactive widgets to existing HTML pages or build full apps with frameworks. Integration with Vite, webpack, Babel, and TypeScript is standard. Works well with headless CMSs, REST and GraphQL APIs, and serverless backends.