Vue.js 3 and Internationalization: Developing Multilingual Applications

Anton Ioffe - December 24th 2023 - 10 minutes read

Welcome to the linguistic kaleidoscope of web development—where crafting multilingual applications is both an art and a technical marvel. As we dive into the world of Vue.js 3 and its Internationalization plugin (I18n), prepare to journey through the setup, design, and intricacies of building applications that speak globally. From configuring a dynamic locale switcher that adapts to your users' lingual preferences, to mastering the essentials of text translations and fallbacks, we'll guide you through optimizing resource management with lazy loading, and finesse your app's international flair by localizing numbers, dates, and currency. Whether you're a seasoned developer or a curious mind in the coding sphere, join us as we unfold the secrets to transforming your application into a worldwide conversationalist.

Setting Up Vue 3 with I18n for Internationalization

To kickstart the internationalization of your Vue 3 application, you'll first need to include Vue I18n, the official internationalization plugin developed by the Vue team. Begin by installing the package using a package manager like npm or Yarn:

npm install vue-i18n@next


yarn add vue-i18n@next

Once installed, it's standard practice to set up a dedicated i18n.js file where you will instantiate the createI18n function provided by Vue I18n. This facilitates modularity and reusability, allowing you to import your i18n configuration across your Vue components or even in other projects.

In your i18n.js, you will need to define your translations and configure the I18n instance. Here's an example setup:

import { createI18n } from 'vue-i18n';

const messages = {
  en: {
    welcomeMessage: 'Welcome to Vue 3 Internationalization'
  fr: {
    welcomeMessage: 'Bienvenue à l\'internationalisation de Vue 3'
  // Add more languages here

const i18n = createI18n({
  locale: 'en', // set default locale
  fallbackLocale: 'en', // set fallback locale
  messages // set locale messages

export default i18n;

It's crucial to define both a default locale and a fallback locale within your i18n setup. The default locale is the primary language your application will display. However, there may be instances where a translation key is missing in the user's preferred language. This is where the fallback locale comes into play, providing an essential layer of robustness to your internationalization process. It ensures the user interface remains comprehensible by displaying an alternative known language rather than an error or a blank page.

Integrating the Vue I18n instance into your Vue application is the final step in the initial setup. Modify your main.js or the equivalent entry file to include the I18n instance:

import { createApp } from 'vue';
import App from './App.vue';
import i18n from './i18n';

const app = createApp(App);

With this, your Vue 3 application is now primed for internationalization, setting you on a clear path toward more complex localization tasks such as adding pluralization, datetime, and number localization. Proper configuration from the outset ensures scalability and ease of maintenance as your application grows and requires additional language support.

Designing a Dynamic Locale Switcher in Vue 3

When designing a dynamic locale switcher in Vue 3, attention must be given to the reactivity and ease of use from the user's perspective. A common component that emerges in this scenario is a LanguageSwitcher. It presents an array of available locales and provides a mechanism for the user to select their preferred language. The component needs to react seamlessly, updating the application's locale in real-time. Under the hood, Vue's reactivity system, coupled with the Vue I18n plugin, can be leveraged to switch languages instantly by updating the locale property, which triggers a re-render of the interface with the chosen language.

  <select v-model="selectedLocale">
    <option v-for="locale in availableLocales" :key="locale" :value="locale">
      {{ localeDisplayName(locale) }}

import { useI18n } from 'vue-i18n';

export default {
  setup() {
    const { locale, t } = useI18n();
    const availableLocales = ['en', 'es', 'fr']; // Example array of locales

    // Helper to display locale names
    const localeDisplayName = (localeCode) => t(`languageNames.${localeCode}`);

    return {
      selectedLocale: locale,
  watch: {
    selectedLocale(newValue) {
      this.$i18n.locale = newValue; // Reactively updates the application's locale

Changing the application locale dynamically involves more than just re-rendering text. One must consider the user experience implications, like the handling of text directionality and layout adjustments. Locale selection must be persisted across sessions to ensure consistency. Storing the user's locale preference in localStorage ensures the chosen language persists across sessions, providing a seamless experience upon return.

For a more immersive experience, integrating the locale into the application's URL is beneficial. With Vue Router, locale can be captured as a route parameter, which allows language-specific URLs to be created and shared. SEO is improved as search engines can index each language version of the site. Updating the routing on locale change ensures the user can navigate consistently within their selected language.

// Vue Router setup with locale as a route parameter
const router = createRouter({
  history: createWebHistory(),
  routes: [
      path: '/:locale',
      component: App,
      beforeEnter: (to, from, next) => {
        const locale = to.params.locale;
        if (availableLocales.includes(locale)) {
          if (i18n.locale !== locale) {
            i18n.locale = locale;
        } else {
          // Redirect to default locale if the one provided is unavailable
          return next({ path: `/${i18n.locale}` }); 
        next(); // Proceed with the route
    // ... additional routes

Maintaining locale state while ensuring a responsive and user-friendly interface involves careful integration of Vue I18n and Vue Router. A dynamic LanguageSwitcher enables real-time updates with minimal performance impact, prioritizing efficient integration without compromising application speed. It accounts for persistence to maintain user choice across sessions and manages URL updates to enhance shareability and search engine visibility. Through this, a Vue 3 application not only becomes multilingual but elevates user experience through thoughtful design.

Internationalization Essentials: Keys, Translations, and Fallbacks

In modern web development, handling multiple languages within an application requires a robust internationalization strategy. A fundamental element of such a strategy in Vue.js 3 is the organization and management of translation keys. These keys serve as unique identifiers that map to locale-specific text values. While constructing your application, it’s essential to structure your keys in a logical, hierarchical manner that corresponds to UI components or thematic groupings, which significantly streamlines the localization process.

const messages = {
    en: {
        navigation: {
            home: 'Home',
            about: 'About',
            contact: 'Contact'
        messages: {
            welcome: 'Welcome to our website!'
    es: {
        // Spanish translations...

Leveraging interpolation is a powerful feature of Vue I18n that inserts dynamic content into translations. This enables your application to display user-specific data or adapt the displayed information based on runtime conditions, thus making your UI more interactive and personalized. It's crucial to escape user-provided data within interpolation to prevent XSS attacks and to ensure that the interpolation expressions are concise to maintain readability.

const userWelcome = this.$t('messages.welcome', { username: userName });

Pluralization adds another layer of complexity. Different languages have different rules for how items are counted, and Vue I18n allows for nuanced pluralization management. By defining custom pluralization rules or using the provided utilities, your application can accurately reflect the grammar rules of the user's locale. This level of attention to proper plural forms will sharpen the user experience and elevate the perceived quality of your app.

const itemTranslation = this.$tc('item', itemCount, { count: itemCount });

Implementing a fallback mechanism ensures that your application can handle missing translations gracefully. By setting up a hierarchical fallback system, your app can attempt to find the best match for a missing translation, starting from the most specific to the most general locale, and ultimately falling back to a predetermined default language. This approach not only maintains a fluid user experience but also aids the development process by making it immediately apparent when a translation is missing.

if(this.$te('missing.key')) {
    console.log('Here\'s your translation', this.$t('missing.key'));
} else {
    console.log('Can\'t find this translation!');

When it comes to handling translations, a common mistake arises from failing to externalize all strings. Developers sometimes hardcode strings that they believe won't need translation, such as error codes or technical terms. However, every piece of text should be treated as potentially translatable to accommodate future requirements. Hardcoded strings can become an obstacle, so it is vital to maintain consistency and put every UI string through the translation process.

In conclusion, consider the nuanced behaviors of languages when developing multilingual applications. How does your app handle languages with different pluralization rules or contextual translations? Are there areas where a translation key has inadvertently been overlooked? Through thoughtful implementation and best practices around keys, translations, and fallbacks, you can pave the way for a truly internationalized Vue.js application.

Leveraging Lazy Loading for Efficient Resource Management

To address the inefficiency of loading all translation files at once in multilingual applications, lazy loading presents a viable solution. Lazy loading in the context of Vue.js 3 internationalization involves dynamically importing translation files based on the user's selected language, rather than loading them all during the initial application load. This approach significantly reduces the initial load time and bandwidth consumption, as only the necessary language files are fetched and parsed.

When a user changes their language preference, an event triggers the loading of the associated translation file. This can be achieved by utilizing the dynamic import feature available in modern JavaScript. The language files can be housed in separate chunks, and the appropriate file is loaded only upon request. The below code snippet illustrates how you might implement this in a Vue.js application:

const loadLocaleMessages = async (locale) => {
  const messages = await import(/* webpackChunkName: "locale-[request]" */ `./locales/${locale}.json`);
  i18n.setLocaleMessage(locale, messages.default);
  return nextTick();

This asynchronous function loadLocaleMessages is called when the user switches languages, dynamically importing the relevant locale.json file, and updating the Vue i18n instance with the new messages.

However, developers should be cautious of over-segmenting the language files. If the application has a high number of very small translation files, the overhead of HTTP requests might outweigh the benefits of lazy loading. It's a delicate balance: chunking language files just enough to maintain performance without causing excessive requests.

Furthermore, the caching strategy must be well-planned to prevent re-fetching language files unnecessarily. It is important to ensure that once a language file is loaded, it remains available for subsequent visits or language switches during the same session. Developers should also consider the user experience during the loading of new language files. Indications such as a loader or disabled state can provide feedback to users that a language change is being processed.

To conclude, lazy loading is a powerful feature that, when implemented properly, greatly optimizes resource management in internationalized Vue.js 3 applications. It provides an on-demand resource loading strategy that aligns with the user's needs and expectations. The key takeaway is to balance the granularity of language chunks, manage caching efficiently, and maintain a seamless user experience during language switches.

Advanced Localization Techniques for Numbers, Dates, and Currency

When dealing with numbers and currencies in a multilingual application, localization is crucial to provide context-appropriate formats for users. Vue I18n's number formatting capabilities are robust, allowing developers to tailor numerical outputs according to locale specifications. For instance, the separation of thousands and decimal points varies between cultures. Here's how you might set up locale-specific formatting rules for numbers within your Vue application's I18n configuration:

const numberFormats = {
  'en-US': {
    decimal: {
      style: 'decimal', minimumFractionDigits: 2, maximumFractionDigits: 2
    currency: {
      style: 'currency', currency: 'USD'
  'de-DE': {
    decimal: {
      style: 'decimal', minimumFractionDigits: 2, maximumFractionDigits: 2
    currency: {
      style: 'currency', currency: 'EUR', currencyDisplay: 'symbol' // Displays the currency symbol instead of the code

By defining such rules within your Vue I18n setup, you can utilize the $n function in templates to format numbers consistently across locales:

<span>{{ $n(123456.789, 'currency') }}</span> <!-- Will output $123,456.79 in en-US or 123.456,79 € in de-DE -->

For date and time localization, Vue I18n offers similar flexibility. You should define dateFormats objects within your application's i18n setup, which outline how dates should be displayed based on the user's locale.

const dateTimeFormats = {
  'en-US': {
    short: {
      year: 'numeric', month: 'short', day: 'numeric'
    long: {
      year: 'numeric', month: 'long', day: 'numeric', weekday: 'long'
  'ja-JP': {
    short: {
      year: 'numeric', month: 'numeric', day: 'numeric'

Using Vue I18n's $d function, it becomes trivial to present users with dates in a familiar format, enhancing the user experience significantly:

<span>{{ $d(new Date(), 'short') }}</span> <!-- Outputs "Jan 1, 2023" in en-US or "2023/1/1" in ja-JP -->

Custom formatters are another powerful feature that Vue I18n provides for developers who have complex localization needs. One might need to create a custom formatter if the built-in capabilities do not meet the precise formatting requirements of the application. Custom formatters must comply with the API expectation of Vue I18n, accepting a locale, a fallback, and a host of formatting options to deliver properly localized content.

Lastly, it's important to address common mistakes related to localization in Vue. Developers sometimes neglect to provide a comprehensive set of rules within their numberFormats and dateTimeFormats, leading to inconsistent user experiences. Ensure that each locale your application supports has a corresponding and complete set of formatting rules. Also, when implementing custom formatters, meticulously test them across all supported locales to prevent unexpected behaviors or formatting issues.

By taking the time to master these advanced localization techniques, senior developers can build Vue.js applications that feel native to users from various cultures and regions. How might you incorporate these techniques into your current project to enhance its international appeal?


In this article, the author explores Vue.js 3 and its Internationalization plugin (I18n) for developing multilingual applications. The article covers topics such as setting up Vue 3 with I18n, designing a dynamic locale switcher, internationalization essentials like keys, translations, and fallbacks, leveraging lazy loading for efficient resource management, and advanced localization techniques for numbers, dates, and currency. The key takeaways include the importance of proper setup and configuration for internationalization, the need for a dynamic locale switcher, the use of interpolation and pluralization for translations, the benefits of lazy loading for resource management, and the significance of localization for numbers, dates, and currency. The article challenges readers to incorporate these techniques into their own projects to enhance their international appeal.

Don't Get Left Behind:
The Top 5 Career-Ending Mistakes Software Developers Make
FREE Cheat Sheet for Software Developers