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Seamless Flutter Localization with .arb Support ​

Translate your Flutter applications across all platforms with Lingo.dev's native support for Application Resource Bundle (.arb) files.

Quick Setup ​

Configure your Flutter project in three simple steps:

  1. Create an i18n.json configuration file
  2. Define your source and target languages
  3. Point to your .arb files using the [locale] placeholder
json
{
  "version": 1.2,
  "locale": {
    "source": "en",
    "targets": ["es", "fr", "de"]
  },
  "buckets": {
    "flutter": {
      "include": ["lib/l10n/[locale].arb"]
    }
  }
}

TIP

The [locale] placeholder automatically expands to the appropriate language code for each target language.

Understanding .arb Files ​

Flutter's .arb format combines simple translations with powerful metadata:

json
{
  "helloWorld": "Hello World!",
  "@helloWorld": {
    "description": "The conventional newborn programmer greeting"
  },
  "welcomeUser": "Welcome, {username}!",
  "@welcomeUser": {
    "description": "A welcome message",
    "placeholders": {
      "username": {
        "type": "String",
        "example": "John Doe"
      }
    }
  },
  "itemCount": "{count, plural, =0{No items} =1{1 item} other{{count} items}}",
  "@itemCount": {
    "description": "A message showing the number of items",
    "placeholders": {
      "count": {
        "type": "num",
        "format": "compact"
      }
    }
  }
}

This structure provides:

  • Basic translations: Simple key-value pairs
  • Contextual descriptions: Metadata for each string
  • Dynamic placeholders: Variables within strings
  • Pluralization rules: Different forms based on quantity

One Command Translation ​

Translate all your Flutter strings with a single command:

bash
npx lingo.dev@latest i18n

This automatically:

  • Processes your source .arb file
  • Preserves all metadata and placeholders
  • Creates or updates target language files
  • Maintains the correct .arb structure

Smart Format Handling ​

Lingo.dev intelligently processes all aspects of .arb files:

1. Complete Structure Preservation ​

  • Metadata: All descriptions and placeholder information remain intact
  • Formatting: JSON structure and indentation are maintained
  • Comments: Any JSON comments are preserved

2. Advanced Translation Features ​

  • Placeholders: Variables like {username} are properly maintained
  • Pluralization: All quantity variations are correctly translated
  • ICU Message Format: Complex message patterns are handled appropriately

Developer Best Practices ​

Improve Translation Quality ​

  1. Add Descriptions: Always include the description field for context

    json
    "welcomeMessage": "Welcome to our app!",
"@welcomeMessage": {
  "description": "Shown on the first screen after login"
}

  2. Provide Examples: For placeholders, include example values

    json
    "placeholders": {
  "username": {
    "example": "JohnDoe123"
  }
}

Optimize Your Workflow ​

  1. Consistent Naming: Use predictable key patterns like screen_element_action

  2. Multiple Files: Split large apps into logical sections

    json
    "flutter": {
  "include": [
    "lib/l10n/[locale].arb",
    "lib/l10n/[locale]_settings.arb"
  ]
}

  3. Integration Testing: Verify translations with Flutter's localization testing tools

By integrating Lingo.dev into your Flutter development workflow, you maintain all the benefits of Flutter's internationalization system while gaining powerful AI-driven translation capabilities.