What is the difference between React Native and React?

React is a JavaScript library for building web user interfaces — it renders to the browser DOM. React Native uses the same React paradigm (components, hooks, state, props, JSX) but renders to native mobile UI instead of the browser DOM. Key similarities: component-based architecture, JSX syntax, hooks (useState, useEffect, useContext, useCallback, useMemo), props and state, same JavaScript, same Redux/Zustand/Recoil state management libraries, same testing patterns. Key differences: (1) No HTML tags: React Native uses View instead of div, Text instead of p/span/h1, Image instead of img, TextInput instead of input; (2) No CSS: React Native uses a JavaScript-based StyleSheet API. Subset of CSS — Flexbox (default), no grid, no CSS cascade; (3) No browser APIs: no window, document, localStorage. Use AsyncStorage, platform APIs; (4) Platform-specific code: some components/APIs differ per platform (iOS vs Android). Use Platform.OS or .ios.js/.android.js file extensions; (5) Navigation: browser has built-in URL routing; React Native needs a library (React Navigation, Expo Router); (6) Performance model: React targets 60fps DOM updates; React Native targets 60fps native rendering across a JS-native bridge. Code that's valid in one is NOT automatically valid in the other.