Fastlane Plugin for Translating iOS Apps

3 hours ago 4

Automatically translate iOS Localizable.xcstrings files using DeepL API. This plugin helps you efficiently manage app localization by translating untranslated strings while preserving your existing translations.

Language selection with progress: Shows translation completeness for each language
Smart targeting: Only translates missing strings, preserves existing translations
Formality options: Formal/informal translation styles for supported languages
Context-aware translation: Uses xcstrings comments to improve translation quality
Progress tracking: Resume interrupted translations without starting over
Automatic backups: Safe translation with rollback capability
Error recovery: Handle API failures gracefully with retry options

Install from RubyGems (Recommended)

fastlane add_plugin translate

Install from GitHub (Latest Development Version)

Add to your Gemfile:

gem "fastlane-plugin-translate", git: "https://github.com/tijs/fastlane-plugin-translate"

Then run:

Get a DeepL API key from https://www.deepl.com/pro#developer
Set your API key as an environment variable:

export DEEPL_AUTH_KEY="your-deepl-api-key-here"

After installation, create a lane in your Fastfile and run it:

Simple dedicated lane:

lane :translate do translate_with_deepl end

Within complex workflows:

lane :prepare_release do build_app translate_with_deepl(target_language: "de") upload_to_testflight slack(message: "New build with German translations available!") end

# Translate to German translate_with_deepl(target_language: "de") # Translate to French with formal style translate_with_deepl( target_language: "fr", formality: "more" )

# Full configuration example translate_with_deepl( xcstrings_path: "./MyApp/Localizable.xcstrings", target_language: "es", formality: "prefer_more", batch_size: 15, free_api: true )

The plugin supports all languages available in both Apple's App Store Connect and DeepL API:

🇩🇪 German (de) - supports formality
🇫🇷 French (fr) - supports formality
🇮🇹 Italian (it) - supports formality
🇪🇸 Spanish (es) - supports formality
🇳🇱 Dutch (nl) - supports formality
🇵🇱 Polish (pl) - supports formality
🇵🇹 Portuguese (pt-BR, pt-PT) - supports formality
🇯🇵 Japanese (ja) - supports formality
🇷🇺 Russian (ru) - supports formality
🇬🇧 English (en-US, en-GB)
🇨🇳 Chinese (zh-Hans, zh-Hant)
🇰🇷 Korean (ko)
And many more...

Languages marked with "supports formality" offer formal/informal translation options

Parameter Description Default Required

api_token	DeepL API authentication key	ENV['DEEPL_AUTH_KEY']	Yes
xcstrings_path	Path to Localizable.xcstrings file	Auto-detected	No
target_language	Target language code (e.g., "de", "fr")	User prompted	No
batch_size	Number of strings per API call	20	No
free_api	Use DeepL Free API endpoint	false	No
formality	Translation formality level	Auto-detected	No

For supported languages, you can specify:

default - Standard formality
more - More formal language
less - Less formal language
prefer_more - Formal if available, otherwise default
prefer_less - Informal if available, otherwise default

🔍 Found xcstrings file: ./Kilowatt/Localizable.xcstrings ✅ DeepL API key validated 💾 Backup created: ./Kilowatt/Localizable.xcstrings.backup_20241201_143022 📋 Available languages for translation: 1. German (de): 45.2% translated (127 remaining) [supports formality] 2. French (fr): 21.8% translated (220 remaining) [supports formality] 3. Spanish (es): 18.1% translated (231 remaining) [supports formality] 🎭 German supports formality options. Choose style: → more (formal) 🔄 Translating from EN to DE 📝 Found 127 untranslated strings 🔄 Translating batch 1/7 (20 strings)... ✅ Batch 1 completed (20 strings) 🔄 Translating batch 2/7 (20 strings)... ✅ Batch 2 completed (20 strings) ... 📝 Updating xcstrings file with 127 translations... 💾 Updated xcstrings file ✅ Updated xcstrings file is valid JSON 🎉 Translation completed! 📊 Translated 127 strings for German (de) 📄 Backup saved: ./Kilowatt/Localizable.xcstrings.backup_20241201_143022 🗑️ You can delete the backup after verifying results

The plugin provides comprehensive error recovery:

⚠️ Rate limit exceeded for batch 3/10 1. Wait 60s and retry 2. Skip this batch 3. Abort translation

❌ Translation error for batch 2/10: Network timeout 1. Skip this batch 2. Retry batch 3. Abort translation

❌ DeepL quota exceeded. Upgrade your plan or wait for reset.

The action sets the following shared values for use in other lanes:

TRANSLATE_WITH_DEEPL_TRANSLATED_COUNT - Number of translated strings
TRANSLATE_WITH_DEEPL_TARGET_LANGUAGE - Target language code
TRANSLATE_WITH_DEEPL_BACKUP_FILE - Path to backup file

lane :translate_and_notify do count = translate_with_deepl(target_language: "de") slack( message: "✅ Translated #{count} German strings!", channel: "#localization" ) end

The plugin automatically saves translation progress:

📈 Found existing progress: 45 strings translated Continue from where you left off? 1. Yes, continue 2. No, start fresh

Progress files are automatically cleaned up after successful completion.

When xcstrings files contain comments, they're used as translation context:

{ "Hello World": { "comment": "Greeting message shown on app launch", "localizations": { ... } } }

This comment becomes context for better translation quality.

Ruby >= 2.6
Fastlane >= 2.0.0
DeepL API account (Free or Pro)

Clone the repository
Run bundle install

Run the full test suite:

Run specific test files:

bundle exec rspec spec/translate_with_deepl_action_spec.rb bundle exec rspec spec/language_registry_spec.rb bundle exec rspec spec/deepl_language_mapper_spec.rb

Run RuboCop for style checking:

Auto-fix correctable issues:

To test the plugin manually with a real project:

# Export your DeepL API key export DEEPL_AUTH_KEY="your-api-key-here" # Test the plugin bundle exec fastlane translate_with_deepl

Ruby >= 3.4
Fastlane >= 2.0.0
DeepL API account (Free or Pro) for manual testing

For bugs, feature requests, or questions, please create an issue.

This project is licensed under the MIT License - see the LICENSE file for details.

fastlane is the easiest way to automate beta deployments and releases for your iOS and Android apps. To get started with fastlane, check out fastlane.tools.

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