i18n-js

i18n-js is a lightweight JavaScript/TypeScript library for internationalization (i18n) and localization (l10n). Version 4.5.3 is stable with regular updates. It provides interpolation, pluralization, and date/number formatting. Unlike react-i18next or i18next, i18n-js is framework-agnostic and simple, focusing on minimal overhead and ease of use. It supports CommonJS and ESM, has TypeScript definitions built-in, and works in both Node.js and browser environments. Key differentiators are its small size (~5 KB gzipped), no dependencies beyond the locale data, and a familiar Rails-style I18n API.