Use the locale prop with the locale you want to use from @nuxt/ui/locale:
<script setup lang="ts">
import { fr } from '@nuxt/ui/locale'
</script>
<template>
  <UApp :locale="fr">
    <NuxtPage />
  </UApp>
</template>
You can create your own locale using the defineLocale composable:
<script setup lang="ts">
import type { Messages } from '@nuxt/ui'
const locale = defineLocale<Messages>({
  name: 'My custom locale',
  code: 'en',
  dir: 'ltr',
  messages: {
    // implement pairs
  }
})
</script>
<template>
  <UApp :locale="locale">
    <NuxtPage />
  </UApp>
</template>
code parameter, there you need to pass the iso code of the language. Example:hi Hindi (language)de-AT: German (language) as used in Austria (region)You can customize an existing locale by overriding its messages or code using the extendLocale composable:
<script setup lang="ts">
import { en } from '@nuxt/ui/locale'
const locale = extendLocale(en, {
  code: 'en-GB',
  messages: {
    commandPalette: {
      placeholder: 'Search a component...'
    }
  }
})
</script>
<template>
  <UApp :locale="locale">
    <NuxtPage />
  </UApp>
</template>
To dynamically switch between languages, you can use the Nuxt I18n module.
pnpm add @nuxtjs/i18n
yarn add @nuxtjs/i18n
npm install @nuxtjs/i18n
bun add @nuxtjs/i18n
nuxt.config.tsexport default defineNuxtConfig({
  modules: [
    '@nuxt/ui',
    '@nuxtjs/i18n'
  ],
  css: ['~/assets/css/main.css'],
  i18n: {
    locales: [{
      code: 'de',
      name: 'Deutsch'
    }, {
      code: 'en',
      name: 'English'
    }, {
      code: 'fr',
      name: 'Français'
    }]
  }
})
locale prop using useI18n<script setup lang="ts">
import * as locales from '@nuxt/ui/locale'
const { locale } = useI18n()
</script>
<template>
  <UApp :locale="locales[locale]">
    <NuxtPage />
  </UApp>
</template>
Each locale has a dir property which will be used by the App component to set the directionality of all components.
In a multilingual application, you might want to set the lang and dir attributes on the <html> element dynamically based on the user's locale, which you can do with the useHead composable:
<script setup lang="ts">
import * as locales from '@nuxt/ui/locale'
const { locale } = useI18n()
const lang = computed(() => locales[locale.value].code)
const dir = computed(() => locales[locale.value].dir)
useHead({
  htmlAttrs: {
    lang,
    dir
  }
})
</script>
<template>
  <UApp :locale="locales[locale]">
    <NuxtPage />
  </UApp>
</template>
 By default, the en locale is used. 
arazbgbncackbcsdadede-CHelenesetfa-IRfifrhehihrhuhyiditjakakkkmkokylbltmnmsnb-NOnlplptpt-BRroruskslsvthtjtrug-CNukuruzvizh-CNzh-TWsrc/runtime/locale/. nuxt-ui CLI to create a new locale: nuxt-ui make locale --code "en" --name "English"