next-tongue

Compiler-first, type-safe i18n for the Next.js 16 App Router. Works with Turbopack, keeps the locale in route params, zero dependencies beyond next and react.

Beta 0.9 — public API is frozen. See API freeze.

Install

npm install next-tongue
npx tongue init

Requires Next.js ≥ 16 (App Router) and React ≥ 19.

Quick start

// tongue.config.ts
import { defineConfig } from 'next-tongue/config';

export default defineConfig({
  locales: ['en', 'de'],
  defaultLocale: 'en',
  messages: './messages/{locale}.json',
});

// next.config.ts
import { withTongue } from 'next-tongue/next';

export default withTongue({ cacheComponents: true });

// proxy.ts — locales + defaultLocale are required
import { createProxy } from 'next-tongue/proxy';

export const proxy = createProxy({
  locales: ['en', 'de'],
  defaultLocale: 'en',
  prefix: 'as-needed',
});
export const config = { matcher: ['/((?!api|_next|.*\\..*).*)'] };

// app/[locale]/page.tsx
import { getT } from 'next-tongue/server';

export default async function Page({
  params,
}: {
  params: Promise<{ locale: string }>;
}) {
  const { locale } = await params;
  const t = await getT(locale, 'home');
  return <h1>{t('title')}</h1>;
}

Package exports

| Import | Use | |---|---| | next-tongue/config | defineConfig | | next-tongue/next | withTongue | | next-tongue/server | getT, getFormat, localeParams, … | | next-tongue/client | TongueProvider, useT, … | | next-tongue/proxy | createProxy | | next-tongue/navigation | createNavigation | | next-tongue/testing | test helpers |

CLI: tongue build | check | extract | init | export | import | report | translate | migrate

Docs

• Getting started
• Configuration
• CLI
• Migration from next-intl
• Roadmap

License

MIT © Louis Wright