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How does Angular handle internationalization (i18n)?

Angular provides a robust built-in internationalization (i18n) framework to help developers build multilingual applications. Here's how Angular handles i18n:

How does Angular handle internationalization (i18n)?

🌐 1. Built-In i18n Support

Angular offers native support for i18n through:

  • The @angular/localize package

  • Markup in templates using the i18n attribute

  • Compiler-level extraction and localization

🔤 2. Marking Text for Translation

You use the i18n attribute in templates to mark static text for translation:

<h1 i18n>Welcome to our site!</h1>

You can also add meaning and description:

<h1 i18n="site-header|Text displayed on homepage">Welcome</h1>

✅ This metadata helps translators understand context.

📦 3. Extracting Translatable Strings

Run this command to extract messages:

ng extract-i18n

This generates a messages.xlf or messages.json file containing all marked strings.

🌍 4. Translating and Managing Files

  • Translators provide localized versions of the file (e.g., messages.fr.xlf for French).

  • Tools like POEditor, Crowdin, or Lokalise can manage translations.

⚙️ 5. Building with Locales

To serve different locales, build the app with the appropriate translation file:

ng build --localize

You define locales and translation files in angular.json:

"projects": {
  "your-app": {
    "i18n": {
      "sourceLocale": "en-US",
      "locales": {
        "fr": "src/locale/messages.fr.xlf",
        "es": "src/locale/messages.es.xlf"
      }
    }
  }
}

This builds multiple versions of the app, one per language.

🧠 6. Runtime vs. Compile-Time i18n

Angular’s i18n system is compile-time by default, which means:

  • Translations are embedded into separate builds

  • Each language has its own bundle

For runtime translation, third-party libraries like ngx-translate are used when:

✅ Best Use Cases for Angular's Built-In i18n:

  • SEO-friendly apps

  • Static content-heavy apps

  • Apps where language is chosen at install/load time

🔄 When to Use ngx-translate:

  • Dynamic language switching

  • Translations from external sources or at runtime

  • Apps with lots of user-generated content

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