i18next

Overview

i18next is the most popular JS i18n framework. Works with React, Vue, Angular, Node.js. Features: namespace splitting, lazy loading, plurals, interpolation, context, and backend plugins for remote translations.

Instructions

Step 1: React Setup

import i18n from 'i18next'
import { initReactI18next } from 'react-i18next'
import HttpBackend from 'i18next-http-backend'
import LanguageDetector from 'i18next-browser-languagedetector'

i18n.use(HttpBackend).use(LanguageDetector).use(initReactI18next).init({
  fallbackLng: 'en',
  supportedLngs: ['en', 'de', 'fr', 'ja'],
  ns: ['common', 'dashboard'],
  defaultNS: 'common',
  backend: { loadPath: '/locales/{{lng}}/{{ns}}.json' },
})

Step 2: Usage

import { useTranslation, Trans } from 'react-i18next'

function Dashboard() {
  const { t } = useTranslation('dashboard')
  return (
    <div>
      <h1>{t('welcome', { name: 'Alice' })}</h1>
      <p>{t('projects', { count: 5 })}</p>
      <Trans i18nKey="terms">Agree to <a href="/terms">Terms</a>.</Trans>
    </div>
  )
}

{
  "welcome": "Welcome back, {{name}}!",
  "projects_one": "You have {{count}} project",
  "projects_other": "You have {{count}} projects"
}

Guidelines

• Split translations into namespaces by feature — don't load everything.
• Use _one/_other suffixes for plurals.
• <Trans> for translations with embedded JSX.
• Language detection: browser → URL → cookie → localStorage.
• For SSR: pass language from server to avoid hydration mismatch.