ai-l10n

AI-powered translation for app localization. Automatically translate your i18n files to 165+ languages using AI. Supports JSON and Flutter ARB formats with intelligent project structure detection.

Powered by l10n.dev

Features

• 🤖 AI-Powered Translations - Context-aware translations using advanced AI
• 🌍 165 Languages - Translate to any of 165 supported languages with varying proficiency levels
• 📁 Smart Detection - Automatically detects target languages from your project structure
• 🔄 Incremental Updates - Translate only new strings while preserving existing translations
• 🔒 Type Safety - Preserves JSON data types—numbers stay numbers, booleans stay booleans, null values are maintained
• 🎯 Multiple Formats - Supports JSON and Flutter ARB files with full metadata handling
• ⚙️ Flexible Configuration - Use via CLI, programmatically, or in CI/CD pipelines
• 🌐 i18next Plural Forms Support - Automatically generates all required plural form strings with correct suffixes. For languages with complex pluralization rules (like Russian, Arabic, or Polish), ensures every necessary form is created
• 🛠️ Developer-Friendly - Preserves placeholders, HTML tags, and formatting while adapting dates and numbers to target locales. Intelligently avoids translating proper names, URLs, and technical terms. Learn more about I18N Translation Using AI
• 🕵️ Smart Error Detection & Chunking - Automatically detects and retries if placeholders or formatting are lost. For large files, splits content into manageable chunks while maintaining context. Prevents issues common with direct AI uploads (Claude/GPT) where exceeding ~16,000 characters causes content loss
• 🔍 Content Filtering - Automatic content filtering at moderate sensitivity. Filtered strings saved separately in i18n JSON format for review
• 📊 Usage Tracking - Monitor character usage and remaining balance
• 💰 Free Tier - Get 30,000 characters free every month

Installation

For CLI + Programmatic (SDK)

npm install ai-l10n

For SDK Only

npm install ai-l10n-sdk

Getting Started

1. Get Your API Key

Get your free API key from l10n.dev/ws/keys

2. Configure API Key

You can provide your API key in three ways:

Option A: Save it globally

npx ai-l10n config --api-key YOUR_API_KEY

Option B: Use environment variable

export L10N_API_KEY=your_api_key_here

Option C: Pass it directly in code or CLI

npx ai-l10n translate path/to/file.json --api-key YOUR_API_KEY

3. Translate Your Files

Basic Translation

# Auto-detect target languages from project structure
npx ai-l10n translate path/to/en.json

# Specify target languages
npx ai-l10n translate path/to/en.json --languages es,fr,de

# Update existing files with only new translations
npx ai-l10n translate path/to/en.json --update

Advanced Options

npx ai-l10n translate ./locales/en.json \
  --languages es,fr,de \
  --plural \                    # Generate plural forms (adds suffixes, e.g., for i18next)
  --shorten \                   # Use shortening
  --no-contractions \           # Don't use contractions (e.g., "don't" vs "do not")
  --update \                    # Update existing files only
  --verbose                     # Detailed logging

Batch Translation

Create a config file translate-config.json:

[
  {
    "sourceFile": "./locales/en/common.json",
    "targetLanguages": ["pl", "ru", "ar"],
    "generatePluralForms": true,
    "translateOnlyNewStrings": true
  },
  {
    "sourceFile": "./locales/en/admin.json",
    "targetLanguages": ["pl", "ru", "ar", "de"]
  }
]

Run batch translation:

npx ai-l10n batch translate-config.json

Configuration Management

# View current API key status
npx ai-l10n config

# Set API key
npx ai-l10n config --api-key YOUR_API_KEY

# Clear API key
npx ai-l10n config --clear

Programmatic Usage

import { AiTranslator } from 'ai-l10n';

const translator = new AiTranslator();

const result = await translator.translate({
  sourceFile: './locales/en.json',
  targetLanguages: ['es', 'fr', 'de'],
});

📚 See the ai-l10n-sdk README for:

• Complete API documentation and TypeScript interfaces
• Advanced usage examples
• Custom logger integration
• Error handling and type definitions

NPM Scripts Integration

Add scripts to your package.json:

{
  "scripts": {
    "translate": "ai-l10n translate ./locales/en.json",
    "translate:update": "ai-l10n translate ./locales/en.json --update",
    "translate:all": "ai-l10n batch translate-config.json"
  }
}

Then run:

npm run translate
npm run translate:update
npm run translate:all

CI/CD Integration

GitHub Actions

ai-l10n provides a ready-to-use GitHub Action for automated translations. The action uses the batch command with a config file for flexible, multi-file translation workflows.

Quick Setup:

1. Create a translation config file ai-l10n.config.json in your repository root:

[
  {
    "sourceFile": "./locales/en/common.json",
    "targetLanguages": ["es", "fr", "de"],
    "translateOnlyNewStrings": true
  }
]

2. Add the workflow file:

name: Auto-translate i18n files

on:
  push:
    branches:
      - main
    paths:
      - 'locales/en.json'
      - 'locales/en/**'
      - 'ai-l10n.config.json'

jobs:
  translate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - uses: l10n-dev/ai-l10n@v1
        with:
          api-key: ${{ secrets.L10N_API_KEY }}
          config-file: 'ai-l10n.config.json'
          pull-request: false
          process-own-commits: false

Action Inputs:

| Input | Description | Default | Required | |-------|-------------|---------|----------| | version | L10n.dev CLI version | latest | No | | api-key | L10n.dev Platform API Key | - | No (can use L10N_API_KEY env var) | | config-file | Path to translation config file | ai-l10n.config.json | No | | pull-request | Create PR instead of direct commit | false | No | | commit-message | Commit message | feat: update translations via L10n.dev | No | | pull-request-title | Pull request title | feat: update translations via L10n.dev | No | | commit-author-name | Git commit author name | L10n.dev | No | | commit-author-email | Git commit author email | [email protected] | No | | process-own-commits | Process commits made by this action | false | No | | working-directory | Working directory (for monorepos) | . | No | | skip-setup-node | Skip Node.js setup if already installed | false | No |

📚 More Examples:

• Pull Request workflow - Creates PR for review (recommended for main/master)
• Direct Commit workflow - Commits directly (for feature branches)
• Manual Trigger workflow - Run manually with custom inputs

GitLab CI

translate:
  stage: build
  script:
    - npm install
    - npx ai-l10n translate ./locales/en.json --update
  only:
    changes:
      - locales/en.json
  variables:
    L10N_API_KEY: $L10N_API_KEY

Jenkins

pipeline {
  agent any
  
  environment {
    L10N_API_KEY = credentials('l10n-api-key')
  }
  
  stages {
    stage('Translate') {
      steps {
        sh 'npm install'
        sh 'npx ai-l10n translate ./locales/en.json --update'
      }
    }
  }
}

Project Structure

ai-l10n automatically detects your project structure and generates translations accordingly.

Folder-Based Structure

locales/
  en/
    common.json
    errors.json
  es/                  # Auto-detected
    common.json
    errors.json
  zh-Hans-CN/          # Auto-detected
    common.json

File-Based Structure (JSON)

locales/
  en.json              # Source
  es.json              # Auto-detected
  fr-FR.json           # Auto-detected
  zh-Hans-CN.json      # Auto-detected

File-Based Structure (Flutter ARB)

lib/l10n/
  app_en.arb           # Source
  app_es.arb           # Auto-detected
  app_fr_FR.arb        # Auto-detected
  app_zh_Hans-CN.arb   # Auto-detected

Configuration Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | sourceFile | string | required | Path to source file (JSON or ARB) | | targetLanguages | string[] | auto-detect | Target language codes (e.g., ["es", "fr", "de"]) | | apiKey | string | env/stored | API key for l10n.dev | | generatePluralForms | boolean | false | Generate plural forms with suffixes (e.g., for i18next). Don't use for strict source-to-target mapping | | useShortening | boolean | false | Use shortening in translations | | useContractions | boolean | true | Use contractions in translations (using contractions makes the translation less formal) | | saveFilteredStrings | boolean | true | Save filtered strings (i18n JSON format with source strings excluded due to content policy violations) to separate .filtered file | | translateOnlyNewStrings | boolean | false | Update existing files with only new translations | | verbose | boolean | false | Enable detailed logging |

Content Filtering

The service uses automated content filtering systems configured at moderate sensitivity levels to balance safety with service availability. When content is filtered:

• Filtered strings are saved in i18n JSON format to a .filtered file (if saveFilteredStrings is enabled)
• Content filtering operates automatically and does not constitute editorial control over your content

If strings are filtered, you'll see:

⚠️ X string(s) were excluded due to content policy violations
ℹ️ View content policy at: https://l10n.dev/terms-of-service#content-policy
📝 Filtered strings saved to: path/to/file.filtered.json

Language Support

l10n.dev supports 165+ languages with varying proficiency levels:

• Strong (12 languages): English, Spanish, French, German, Chinese, Russian, Portuguese, Italian, Japanese, Korean, Arabic, Hindi
• High (53 languages): Most European and Asian languages including Dutch, Swedish, Polish, Turkish, Vietnamese, Thai, and more
• Moderate (100+ languages): Wide range of world languages

Language Codes

Use standard language codes (BCP-47 with optional script and region):

• Simple: es, fr, de, ja, zh
• With region: en-US, en-GB, pt-BR, zh-CN
• With script: zh-Hans, zh-Hant
• Full format: zh-Hans-CN

For ARB files, use underscores: en_US, zh_Hans_CN

Troubleshooting

API Key Issues

# Check if API key is configured
npx ai-l10n config

# Set new API key
npx ai-l10n config --api-key YOUR_API_KEY

# Or use environment variable
export L10N_API_KEY=your_api_key_here

No Languages Detected

If auto-detection fails, specify languages explicitly:

npx ai-l10n translate ./locales/en.json --languages es,fr,de

Insufficient Balance

Purchase more characters at l10n.dev/#pricing

Related Projects

• VS Code Extension - Translate directly in VS Code

Support

• 📧 Email: [email protected]
• 🐛 Issues: GitHub Issues
• 📚 API Documentation: l10n.dev/api/doc
• 🌐 Website: l10n.dev

Pricing

• Free Characters: 30,000 characters free every month
• Pay-as-you-go: Affordable character-based pricing with no subscription required
• Current Pricing: Visit l10n.dev/#pricing for up-to-date rates

Privacy & Security

• Secure API Keys: Stored securely in your home directory (~/.ai-l10n/config.json) or via environment variables
• No Data Storage: Source code and translations are not stored on our servers beyond processing time
• Encrypted Communication: All communication with l10n.dev API uses HTTPS encryption
• Privacy First: Built by developers for developers with privacy, reliability, and quality as top priorities

💡 Tip for Large-Files Translation:

This npm package translates files in real-time via the Translate JSON API and does not store your JSON or translations on our servers. For very large files, translation may take several minutes.

On the I18N File Translation page, you can:

• Securely create translation jobs for batch processing
• Set custom terminology for consistent translations
• Monitor progress in real-time
• Download files when complete with full control (delete anytime)

Important: Working with Arrays in JSON

⚠️ When using "Translate Only New Strings": If your JSON contains arrays (not just objects), ensure array indexes in your target file match those in the source file. When adding new strings, always append them to the end of the array.

Example:

// ✅ CORRECT: New items added at the end
// source.json
["Apple", "Banana", "Orange"]

// target.json (existing)
["Manzana", "Plátano"]

// After translation (new item appended)
["Manzana", "Plátano", "Naranja"]

// ❌ INCORRECT: Items inserted in the middle
// This will cause misalignment!
["Apple", "Cherry", "Banana", "Orange"]

For object-based JSON structures (recommended for i18n), this is not a concern as translations are matched by key names.

License

AGPL-3.0

Credits

Powered by l10n.dev - AI-powered localization service