Lazy Loading#

Non-initial locales can be loaded on demand:

const i18n = createI18n({
  locale: "en",
  fallbackLocale: "en",
  messages: {
    en,
    de: () => import("./locales/de"),
    fr: () => import("./locales/fr"),
  },
});

A loader may resolve directly to a message object or to an ES module with a default export. The first successful result is cached. Concurrent requests for the same locale share one promise, while failed requests are removed from the cache and may be retried.

Required eager locales#

The initial locale and fallback locale must be eager message objects:

// Invalid: `t()` is synchronous, so `en` is unavailable for the first render.
createI18n({ locale: "en", fallbackLocale: "en", messages: { en: () => import("./en") } });

This rule is enforced by TypeScript and by runtime validation. To start with a remotely loaded locale, load its messages before calling createI18n().