next-i18next/dist/appRouter/server.d.mts

The easiest way to translate your NextJs apps.

import { FlatNamespace, InitOptions, KeyPrefix, Resource, TFunction, i18n } from "i18next";

//#region src/appRouter/types.d.ts
type ResourceLoader = (language: string, namespace: string) => Promise<any>;
interface I18nConfig {
  /** Supported languages, e.g. ['en', 'de', 'it'] */
  supportedLngs: string[];
  /** Default/fallback language */
  fallbackLng: string;
  /** Default namespace (defaults to 'common') */
  defaultNS?: string;
  /** All known namespaces (defaults to [defaultNS]) */
  ns?: string[];
  /** Path to locale files relative to /public (defaults to '/locales') */
  localePath?: string;
  /** Directory structure pattern (defaults to '{{lng}}/{{ns}}') */
  localeStructure?: string;
  /** File extension (defaults to 'json') */
  localeExtension?: string;
  /** Pre-loaded resources (if provided, skips dynamic loading) */
  resources?: Resource;
  /** Custom resource loader function (overrides localePath) */
  resourceLoader?: ResourceLoader;
  /** Whether to include locale in URL path (defaults to true) */
  localeInPath?: boolean;
  /** When true (and localeInPath is true), the default language has no URL prefix.
   *  e.g. `/about` serves the default language, `/de/about` serves German.
   *  Requests to the explicit default prefix (`/en/about`) are redirected to `/about`. */
  hideDefaultLocale?: boolean;
  /** Cookie name for storing selected language (defaults to 'i18next') */
  cookieName?: string;
  /** Custom header name for passing language to server components (defaults to 'x-i18next-current-language') */
  headerName?: string;
  /** Cookie max age in seconds (defaults to 365 * 24 * 60 * 60) */
  cookieMaxAge?: number;
  /** URL path prefixes to ignore in middleware (defaults to ['/api', '/_next', '/static']) */
  ignoredPaths?: string[];
  /** Base path prefix for middleware to handle (e.g., '/app-router'). When set, the middleware only processes requests under this prefix and locale segments are placed after it. Useful for mixed App Router + Pages Router setups. */
  basePath?: string;
  /** Extra i18next plugins to use */
  use?: any[];
  /** Additional i18next init options (merged into init call) */
  i18nextOptions?: Omit<InitOptions, 'lng' | 'resources' | 'ns' | 'defaultNS' | 'supportedLngs' | 'fallbackLng'>;
  /** Legacy i18n config for Pages Router / next.config.js */
  i18n?: {
    defaultLocale: string;
    locales: string[];
    domains?: {
      defaultLocale: string;
      domain: string;
      http?: true;
      locales?: string[];
    }[];
    localeDetection?: false;
  };
  /** @deprecated Use i18nextOptions instead */
  serializeConfig?: boolean;
  /**
   * Dev-only: when true (and `NODE_ENV !== 'production'`), reload translation
   * resources from the backend before each render so edits to locale files
   * appear without restarting `next dev`. No effect in production builds.
   */
  reloadOnPrerender?: boolean;
  /** Support non-explicit language codes like 'en' matching 'en-US' */
  nonExplicitSupportedLngs?: boolean;
}
type GetTResult<Ns extends FlatNamespace = FlatNamespace, KPrefix = undefined> = {
  t: TFunction<Ns, KPrefix>;
  i18n: i18n; /** The resolved language for the current request */
  lng: string;
};
//#endregion
//#region src/appRouter/server.d.ts
/**
 * Initialize the server-side i18next configuration.
 * Call this once in your root layout or a shared setup file.
 */
declare function initServerI18next(userConfig: I18nConfig): void;
/**
 * Get a translation function for use in Server Components, layouts, and generateMetadata.
 *
 * The underlying i18next instance is a **module-level singleton** that persists across
 * requests. This means custom backends (i18next-http-backend, i18next-locize-backend, etc.)
 * only fetch translations once (or according to their own reloadInterval), not on every request.
 *
 * @example
 * ```tsx
 * import { getT } from 'next-i18next/server'
 *
 * export default async function Page() {
 *   const { t, i18n } = await getT('home')
 *   return <h1>{t('heading')}</h1>
 * }
 * ```
 */
declare function getT<Ns extends FlatNamespace = FlatNamespace, KPrefix extends KeyPrefix<Ns> = undefined>(ns?: Ns | Ns[], options?: {
  keyPrefix?: KPrefix;
  lng?: string;
}): Promise<GetTResult<Ns, KPrefix>>;
/**
 * Extract loaded resources from the server i18next instance for passing to I18nProvider.
 *
 * @example
 * ```tsx
 * const { i18n } = await getT()
 * const resources = getResources(i18n, ['common', 'footer'])
 * return <I18nProvider language={i18n.language} resources={resources}>{children}</I18nProvider>
 * ```
 */
declare function getResources(i18n: i18n, namespaces?: string[]): Resource;
/**
 * Helper for generateStaticParams — returns params for all supported languages.
 *
 * @example
 * ```tsx
 * import { generateI18nStaticParams } from 'next-i18next/server'
 *
 * export async function generateStaticParams() {
 *   return generateI18nStaticParams()
 * }
 * ```
 */
declare function generateI18nStaticParams(): {
  lng: string;
}[];
//#endregion
export { generateI18nStaticParams, getResources, getT, initServerI18next };
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