i18next Internationalization Framework

i18next is a free and open-source internationalization (i18n) framework written in and for JavaScript, providing a complete solution for localizing applications. Created by Jamuhl Manser (jamuhl) and Adriaan Neeleman in 2011, i18next has become the most popular i18n framework for JavaScript/React, used by Atlassian, Microsoft, and thousands of companies. Key features: translation management: translations are stored as JSON key-value pairs, organized by namespaces and languages. The t() function retrieves translations by key (t('greeting') returns the greeting in the current language). Interpolation: dynamic values are inserted into translations (t('welcome', { name: 'John' }) with 'welcome': 'Hello {{name}}'). Pluralization: automatic plural form selection based on count. Supports complex plural rules for different languages (Russian, Arabic, Polish) using the plural suffix system. Formatting: built-in formatting for numbers, dates, and currencies via Intl API integration. Nested keys: translations can be nested ('user.profile.name' traverses { user: { profile: { name: '...' } } }). Namespaces: organize translations into multiple files (common.json, errors.json, dashboard.json) loaded on demand, reducing initial bundle size. Language detection: i18next-browser-languagedetector detects the user's language from browser settings, URL, cookies, or localStorage. Language fallback: if a key is missing in the current language, i18next falls back to a default language. Lazy loading: load translations on demand as users navigate to different sections. Context: context-aware translations (t('item', { context: 'male' })). React integration: react-i18next provides useTranslation hook, Trans component for complex translations with embedded JSX, and I18nextProvider. Backend plugins: load translations from a backend server, localStorage, or filesystem. Server-side rendering support. JavaScript/TypeScript. MIT.