Many developers miss significant iOS internationalization techniques that could boost their app's reach and revenue by a lot. iOS users show higher purchasing power and generate greater App Store revenue compared to Android platforms. Apple paid developers more than $60 billion in 2022 alone. This massive chance requires developers to become skilled at iOS localizable strings, understand Swift localization intricacies, and implement iOS localization best practices beyond simple Xcode localization features.
This complete iOS localization piece will show you hidden features and techniques most developers overlook. Explore culturally adapted metadata translation to streamline this process. You'll learn everything from using locale-specific screenshots that match cultural norms to building a fully localized product page as your first step into international markets. The knowledge you gain will help you revolutionize your app's global presence and realize new revenue streams through the App Store's worldwide reach.
Preparing Your App for iOS Internationalization
Good app internationalization is the foundation for successful iOS localization. Your original setup, before any translation begins, will give you a smoother process later if you structure your code and UI elements with localization in mind.
Separating UI and Code Strings Early
You need to separate user-facing text from your core code for good iOS internationalization. This should happen right from the start—not as an afterthought when you want to go global.
Xcode's Base Internationalization feature automatically extracts UI elements from your code repository, which makes them ready for localization. This creates a structure where localized resources live in language-specific folders (such as en.lproj for English) within your app bundle [1].
To implement this structure:
- Enable "Use Base Internationalization" when setting up your project
- Place your interface files (.storyboard, .xib) in the Base.lproj folder
- Create separate .lproj folders for each target language
- Store translated content in these language-specific folders
This setup comes with clear benefits. Localizers don't have to touch .storyboard and .xib files directly in Interface Builder [2]. Plus, it keeps your app's functionality separate from its user-facing content.
Here's something people often miss: Base Internationalization makes your development more flexible. You can update the base files without touching your localized versions, so you save a lot of development time.
Also, organizing your source code from the start helps you avoid the headache of embedded text strings that become hard to extract later. Rather than hard-coding text, use placeholders that connect to external resource files with your translated content [3].
Using NSLocalizedString vs String(localized:)
iOS developers have two main ways to handle string localization in code: the classic NSLocalizedString macro and the newer Swift-friendly String(localized:) initializer.
NSLocalizedString has been around for years and works like this:
// Basic usage
let welcomeMessage = NSLocalizedString("welcome.message",
comment: "Greeting shown on the home screen")
// With format specifiers
let salesMessage = NSLocalizedString("You have sold 1000 apps in %d months",
comment: "Time to sell 1000 apps")
salesLabel.text = String.localizedStringWithFormat(salesMessage, period)
The best part about NSLocalizedString is that the genstrings tool picks it up automatically and creates .strings files for translation [4]. The comment parameter helps translators understand how and where the string appears in your app.
Apple recommends the String(localized:) initializer for newer iOS apps, especially those targeting iOS 15 and later:
// Basic usage
let welcomeMessage = String(localized: "Buy a book")
// With comments
let exploreTitle = String(localized: "Explore",
comment: "Title of the Explore tab")
This method fits better with Swift's syntax and modern string catalogs. While NSLocalizedString needs an extra step for format strings, String(localized:) handles string interpolation more naturally [5].
Here's what to think about when picking between these approaches:
- Project age and compatibility: Older iOS versions need
NSLocalizedString - Team familiarity: Developers who know Objective-C might prefer
NSLocalizedString - Code consistency: Stick to one approach throughout your project
- Modern features:
String(localized:)works better with Swift's string interpolation and catalogs
Many developers make the mistake of mixing these approaches, which leads to messy localization behavior and harder maintenance. New Swift-only projects usually work better with String(localized:).
Whatever method you pick, keep your localizable strings separate and organized from day one. Try using namespaced keys like "home.button.start-run" instead of default language text as keys. This helps avoid translation issues when different languages need different terms for the same concept [4].
Setting up these internationalization basics early means your app will be ready for multiple languages—making the translation process much easier down the road. Learn more about AI-powered metadata translation.
Managing Translations with Localization Tools
Your app's codebase needs to be ready for internationalization before moving to the next vital phase - managing translations. The quickest way to handle this workflow uses the right tools. These tools let you create an exceptional localized experience without getting bogged down in manual file management.
Uploading .strings and .xliff Files to Lokalise or Smartling
Xcode's powerful "Export For Localization" feature extracts all localizable content from your project automatically. The content comes from strings in your code, stringsdict files, Interface Builder files, and localized assets. No source code modifications are needed [5]. This export creates XLIFF (.xliff) files - the standard format for translation exchange.
Lokalise and Smartling platforms offer these key features:
- File Format Support: Both platforms work with iOS-specific formats like .strings, .xliff, and .stringsdict files. Some Xcode versions include plural strings in .xliff that need extra attention [6].
- Centralized Management: A single place organizes all localization projects and tracks progress across languages [7].
- Translation Memory: The system stores and reuses previous translations to keep terminology consistent [8].
- Collaboration Features: Quality stays high with comment systems, glossaries, and QA checks [8].
Developers working with newer iOS string catalogs (.xcstrings) can now import and export directly on many platforms [9].
Using Visual Context for Accurate Translation
Translators often face the "what am I translating?" challenge. Research shows visual context can cut translation errors by half [10]. Translators need context to understand how strings fit in your UI.
You can provide visual context in several ways:
Screenshots show where strings appear in your app. Most platforms use OCR to detect and link text in images to project strings automatically. This beats manual linking hands down.
Smartling's web proxy options act as translation filters. Translators see exactly where text appears in your interface [10]. This context matters a lot for iOS apps because space limits affect translation length.
Human translators make better choices with visual context than machine translation alone. Machines miss context, cultural nuances, and language subtleties [5]. A translation guide with character names, humor explanations, and common terms helps boost accuracy even more [5].
Automating File Sync with CLI or API
String file handling gets messy as apps grow bigger. CLI tools and API integrations make this process smooth and error-free.
Localization platforms connect to your development environment through powerful APIs and CLIs. You can add string extraction, translation uploads, and completed translation downloads to your CI/CD pipeline [10]. This creates a smooth localization workflow that keeps up with development.
SimpleLocalize shows this with their CLI commands:
simplelocalize upload --apiKey <PROJECT_KEY> --uploadFormat localizable-strings --uploadPath ./{lang}/Localizable.strings
Lokalise's CLI converts between different file formats too. You maintain one source while supporting multiple platforms [11]. Their conversion objects generate different file formats as needed:
localazy download
Many platforms offer GitHub integrations that sync automatically with your repository updates. New strings get identified without manual work. Localization becomes part of your regular product development [10].
These automated workflows make iOS localization faster and more reliable. Your international users get a better experience as a result.
Best Practices for Localizing SwiftUI and UIKit
SwiftUI and UIKit give you different ways to localize your iOS app. They share the same foundation but each framework needs its own approach to handle multiple languages.
Using LocalizedStringKey in SwiftUI Text Views
SwiftUI makes localization easy with its built-in support for LocalizedStringKey. This type looks up localized strings automatically when you pass string literals to SwiftUI views. You can see this in action when you write Text("Hello, World!"). SwiftUI turns this into a LocalizedStringKey that looks through your app's localization files.
This works because LocalizedStringKey follows the [ExpressibleByStringLiteral](https://developer.apple.com/documentation/swiftui/localizedstringkey) protocol, which lets string literals convert automatically [12]. The difference between string literals and variables is worth noting:
- String literals:
Text("hello.world")- Changes toLocalizedStringKeyon its own - String variables:
Text(messageString)- Shows up exactly as written
This leads to one of the most common mistakes in SwiftUI localization. You need to create a LocalizedStringKey yourself when you pass a variable to a Text view if you want it localized [12]. If you don't, SwiftUI will show the string exactly as it is.
You might need to use NSLocalizedString for more complex cases with formatted strings or dynamic content:
// For formatted strings with parameters
Text(String(format: NSLocalizedString("hello", comment: ""), name))
Modern SwiftUI apps that target iOS 15+ can use a better approach with String(localized:) [13]:
Text(String(localized: "welcome.message",
comment: "Greeting shown on home screen"))
Previewing SwiftUI Views in Multiple Locales
Testing your interface in different languages is vital. SwiftUI Previews makes this simple with the locale environment modifier.
Here's how to preview your view in a specific locale:
#Preview("English") {
ContentView()
.environment(.locale, .init(identifier: "en"))
}
#Preview("Spanish") {
ContentView()
.environment(.locale, .init(identifier: "es"))
}
You can also create previews for all supported locales automatically [1]:
static let localizations = Bundle.main.localizations
.map(Locale.init)
.filter { $0.identifier != "base" }
static var previews: some View {
ForEach(localizations, id: .identifier) { locale in
ContentView()
.environment(.locale, locale)
.previewDisplayName(Locale.current.localizedString(
forIdentifier: locale.identifier))
}
}
This code creates previews for each language your app supports and updates them as you add new ones. We filter out the "base" localization to avoid duplicate previews [1].
Avoiding Hardcoded Strings in UIKit
Many iOS apps use UIKit or mix it with SwiftUI. UIKit needs more direct handling to avoid hardcoded strings.
The best way to handle UIKit localization is to use NSLocalizedString for text that users see:
titleLabel.text = NSLocalizedString("welcome.title",
comment: "Main screen welcome message")
A big mistake is putting string values straight into Interface Builder without localization [14]. You can fix this by:
- Making UIKit component subclasses that handle localization on their own
- Using IBInspectable properties to set localization keys in Interface Builder
- Adding a string extension to make localized string access easier
Here's what a localization-ready UILabel subclass looks like:
@IBDesignable class UILocalizedLabel: UILabel {
@IBInspectable var tableName: String?
override func awakeFromNib() {
super.awakeFromNib()
self.text = self.text?.localized(tableName: tableName)
}
}
These techniques help you build an app that works naturally in different languages and feels native to users worldwide.
Handling Dynamic Content and Formatting
Text localization goes beyond just translating static content. You need to handle dynamic content like numbers, dates, and strings with variables carefully. Each locale has its own formatting rules that these elements must follow.
NumberFormatter for Currency and Decimal Localization
Numbers look different in various regions. The number 3,490,000.89 shows up as "3 490 000,89 €" in France and "3.490.000,89 €" in Germany. They use completely different separators and decimal symbols [15].
iOS's NumberFormatter class helps handle these regional differences:
let currencyFormatter = NumberFormatter()
currencyFormatter.usesGroupingSeparator = true
currencyFormatter.numberStyle = .currency
currencyFormatter.locale = Locale.current
// Display price based on user's device settings
let priceString = currencyFormatter.string(from: 9999.99)!
// Shows "$9,999.99" in US, "9 999,99 €" in France
The numberStyle property comes with several options besides .currency, like .decimal, .percent, and .ordinal. Yes, it is worth noting that .decimal style shows numbers based on local formats – changing 123456789 to "123,456,789.00" for US English but "1.234.567.899,00" for Spanish users [16].
Many developers don't realize that number formats link to regions, not languages. You can set the locale explicitly to avoid surprises:
// Force display in specific locale whatever the device settings
currencyFormatter.locale = Locale(identifier: "de_DE")
// Outputs "9.999,99 €" for German format
DateFormatter for Locale-specific Date Display
Dates look different around the world. The DateFormatter class helps solve this:
let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .short
// Automatically formats for the user's locale
let localizedDate = dateFormatter.string(from: Date())
Developers sometimes make the mistake of hardcoding date strings. Using .dateStyle and .timeStyle creates dates that match the user's settings automatically [17].
Template-based formatting gives you more control while keeping locale-specific arrangements:
// Template with year, month, day components
let template = "yMMMMd"
// Get format appropriate for specific locale
let dateFormat = DateFormatter.dateFormat(
fromTemplate: template,
options: 0,
locale: Locale(identifier: "en_US")
)
// Results in "MMMM d, y" for US but "d MMMM y" for UK
This makes dates like "October 15" in US English appear as "15 oktober" in Dutch, matching both order and spelling conventions [18].
Using Format Specifiers in Localizable.strings
Format specifiers let you add dynamic content to localized strings. They start with % followed by type indicators like %s for strings or %d for integers [19].
Positional specifiers are crucial for multilingual apps. Explore AI-powered metadata translation to streamline this process. Translators can rearrange variables to match their language's structure:
// English
"user_task_progress" = "%@ finished %lu out of %lu tasks.";
// Chinese
"user_task_progress" = "%1$@ 完成了 %3$lu 項任務中的 %2$lu 項。";
The numbers (%1$, %2$, etc.) tell which argument goes where, so translators can move variables around without touching your code [20].
Apple provides .stringsdict files to handle plural forms:
<key>user_task_progress</key>
<dict>
<key>NSStringLocalizedFormatKey</key>
<string>%1$@ has finished %2$#@tasks@</string>
<key>tasks</key>
<dict>
<key>NSStringFormatSpecTypeKey</key>
<string>NSStringPluralRuleType</string>
<key>NSStringFormatValueTypeKey</key>
<string>lu</string>
<key>one</key>
<string>%2$lu out of 1 task</string>
<key>other</key>
<string>%2$lu out of %3$lu tasks</string>
</dict>
</dict>
This stringsdict approach handles plural forms smoothly without complex code, keeping grammar correct in all languages [20].
Testing and QA for Localized Apps
Testing localized apps really goes beyond simple string replacement. Quality assurance teams must verify that interfaces work with different text lengths, cultural conventions, and reading directions in a variety of languages.
Exporting and Importing Localizations in Xcode
Xcode makes the localization workflow easier with built-in export and import features. Select your project in the Navigator and choose Product > Export Localizations [2]. Xcode then creates an Xcode Localization Catalog (.xcloc) file for each language [21]. These catalogs contain:
- An XLIFF file with extractable strings from code, storyboards, and XIB files
- Proper .stringsdict plural variants for each language
- Source content files that give context to translators [2]
Translators get better visual context when you enable the "Include screenshots" option during export [2]. The localized content can be reimported through Product > Import Localizations by selecting the updated .xcloc files [21].
Using Xcode Previews and Simulators for Locale Testing
SwiftUI's preview capabilities make locale testing simple. The preview code lets you set locale-specific environment variables:
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
.environment(.locale, .init(identifier: "de"))
}
}
Multiple localizations can be tested at once by creating additional previews with different locale identifiers [22].
Simulator testing provides real-life validation. The app target's scheme settings can be modified to a specific language [23], or you can change the Simulator's system language. System language changes require a Simulator restart, while scheme adjustments only affect your app [23].
Running UI Tests for RTL and LTR Layouts
RTL language support needs extra attention during testing. Xcode offers a "Right-to-Left Pseudolanguage" option in scheme settings that switches your UI to RTL orientation without Arabic or Hebrew translations [24].
SwiftUI developers can force specific views to use RTL direction by changing the layoutDirection environment key:
ContentView()
.environment(.layoutDirection, .rightToLeft)
.environment(.locale, .init(identifier: "de"))
UIKit apps can test RTL layouts by modifying the semanticContentAttribute property of views [25]. RTL testing should verify that:
- Images flip correctly when needed (using
imageFlippedForRightToLeftLayoutDirection) - Navigation flows from right to left properly
- Text aligns according to language direction [25]
Xcode test plans should be configured with different locale settings to find clipping, truncation, or layout issues across languages and devices [5].
App Store Localization and ASO Strategy
Your app's internal localization is perfect. Now it's time to optimize its App Store presence. The product page creates a significant first impression for potential users around the world.
Localizing App Name, Description, and Keywords
App Store lets you localize various metadata elements. You can translate your app's name, subtitle, description, keywords, promotional text, support URL, and "What's New" section [4] into more than 40 languages and locales [4]. This helps you craft messages that resonate with specific markets.
App Store localization needs more than simple translation. Each locale shows different search behaviors that need customized keywords. You can optimize discoverability through App Store Connect's keyword field for each locale [26].
Note that your app's primary language keywords will show up in all locales without localization [26]. You should plan your market priorities based on expansion goals.
Using Locale-specific Screenshots and Previews
Visual assets drive conversion rates on the App Store. Each device size and language can have one to ten screenshots [27] and up to three optional app previews [27].
Your screenshots should reflect these cultural elements for each locale:
- Local currency formats
- Regionally appropriate imagery
- Translated UI elements
- Cultural norms and references
The process to add localized screenshots is simple. Go to App Store Connect, select your app, click the version you want, and use Media Manager to upload assets for each language [4]. App previews always appear before screenshots in the store listing [27].
Using Multi-index Localization for Visibility
Cross-localization offers a powerful way to expand your app's reach. Each App Store territory has one primary language and several supported languages [28]. You can use this feature even without full international expansion.
The US App Store supports ten localizations. English (US) is primary, with Arabic, Chinese (Simplified and Traditional), French, Korean, Portuguese (Brazil), Russian, Spanish (Mexico), and Vietnamese [3] as additional options. Your app can be indexed for keywords in all these languages within the US market.
Fill non-target localizations with content in your target language [28] to implement this strategy. This approach maximizes visibility while keeping conversion rates high. Users see relevant content regardless of which localization brought them to your app.
Conclusion
Our deep dive into iOS localization has revealed many hidden features that most developers miss. Explore global app launch checklist to streamline this process. Quality internationalization is the life-blood of global app success. The process starts with separating UI and code strings early. This lays the groundwork to expand smoothly into the App Store's 175+ regions and 40+ languages.
iOS localization goes nowhere near just translating text. You need a strategic plan to manage translations with tools like Lokalise or Smartling. These tools give visual context to translators and automate file syncing through CLI or API integration. SwiftUI and UIKit frameworks each need different approaches to create natural-feeling localized experiences.
Dynamic content brings its own set of challenges. The right setup of NumberFormatter, DateFormatter, and format specifiers will give your app the ability to show currencies, dates, and variable text correctly in all locales. Testing these features needs a detailed plan. This includes Xcode previews, simulator testing, and specialized UI tests for both LTR and RTL layouts.
Your app's localization should cover its App Store presence too. Explore screenshots that increase conversions to streamline this process. A localized app name, description, and keywords paired with culturally relevant screenshots will substantially boost conversion rates. Multi-index localization strategy can boost your visibility even in single markets.
Quality iOS localization helps realize your app's revenue potential. iOS users' higher purchasing power means good localization associates directly with better global reach and revenue. These hidden localization features will help turn your regional product into a global experience. Your app will connect with users in their native languages while respecting their cultural context and priorities.
Key Takeaways
Master these often-overlooked iOS localization techniques to unlock global revenue potential and reach the App Store's 175+ regions effectively. Learn more about comprehensive localization guide.
• Separate UI strings early: Use Base Internationalization and NSLocalizedString/String(localized:) from project start to avoid costly refactoring later.
• Leverage visual context tools: Upload screenshots to translation platforms like Lokalise or Smartling to reduce translation errors by up to 50%. Learn more about best app store optimization tools.
• Test with SwiftUI Previews: Use environment modifiers to preview multiple locales simultaneously and catch layout issues before release.
• Handle dynamic content properly: Implement NumberFormatter and DateFormatter for locale-specific currency, dates, and number formatting across regions.
• Optimize App Store presence: Localize app metadata, keywords, and screenshots for each market—not just direct translations but culturally relevant content.
• Automate the workflow: Use CLI tools and APIs to sync translations automatically, making localization part of your CI/CD pipeline rather than manual process.
Remember that iOS users have higher purchasing power globally, making quality localization a direct path to increased revenue. These hidden features transform your app from a regional product into a truly global experience that resonates with users in their native languages and cultural contexts.
FAQs
Q1. Explore translate app metadata into 40+ languages to streamline this process. What is the first step in preparing an iOS app for localization? The first step is to separate UI and code strings early in the development process. This involves using Base Internationalization in Xcode and storing localizable content in separate resource files, making it easier to translate and manage different language versions.
Q2. How can developers provide context for translators to improve localization accuracy? Developers can provide visual context by uploading screenshots of the app's interface to localization platforms. This helps translators understand where and how strings appear in the UI, potentially reducing translation errors by up to 50%.
Q3. What's the difference between using NSLocalizedString and String(localized:) for localization? NSLocalizedString is the traditional method that works with older iOS versions and is picked up by the genstrings tool. String(localized:) is a newer Swift-friendly approach recommended for iOS 15 and later, offering better integration with Swift's syntax and modern string catalogs.
Q4. How can developers test their app's localization across different languages? Developers can use SwiftUI Previews to quickly view their app in multiple locales, utilize Xcode's simulator to test in different language settings, and run UI tests specifically designed for both left-to-right and right-to-left layouts.
Q5. What strategies can be used to optimize an app's visibility in the App Store for different locales? To optimize visibility, developers should localize their app's metadata (name, description, keywords) for each target market, use culturally relevant screenshots and previews, and leverage multi-index localization to appear in searches across multiple languages within a single App Store territory.
References
[1] - https://www.avanderlee.com/swiftui/previews-different-states/
[2] - https://developer.apple.com/documentation/xcode/exporting-localizations/
[3] - https://www.apptweak.com/en/aso-blog/how-to-benefit-from-cross-localization-on-the-app-store
[4] - https://www.apptamin.com/blog/how-to-upload-your-localized-assets-on-the-app-store/
[5] - https://developer.apple.com/localization/
[6] - https://help.smartling.com/hc/en-us/articles/360007943754-Mobile-Apps-Overview
[7] - https://lokalise.com/
[8] - https://crowdin.com/
[9] - https://simplelocalize.io/blog/posts/manage-ios-translation-files/
[10] - https://xtm.cloud/blog/app-localization-tools/
[11] - https://localazy.com/blog/tips-for-localizing-multiplatform-apps-localazy-cli?srsltid=AfmBOorAxw7tZYPXsUUhLxrbySroJ2RL_nYicz8qfRUdAUlZOjFW5p0y
[12] - https://developer.apple.com/documentation/swiftui/localizedstringkey
[13] - https://developer.apple.com/videos/play/wwdc2021/10221/
[14] - https://marcosantadev.com/app-localization-tips-swift/
[15] - https://supereasyapps.com/blog/2016/2/8/how-to-use-nsnumberformatter-in-swift-to-make-currency-numbers-easy-to-read
[16] - https://phrase.com/blog/posts/ios-tutorial-internationalization-localization/
[17] - https://medium.com/mobile-app-development-publication/mastering-date-formatting-in-swift-979ffae19ca8
[18] - https://www.donnywals.com/formatting-dates-in-the-users-locale-using-dateformatter-in-swift/
[19] - https://localizely.com/apple-strings-file/
[20] - https://www.oneskyapp.com/academy/learn-ios-localization/2-format-strings-plurals/
[21] - https://transolve.io/how-to-import-and-export-localization-files-in-xcode/
[22] - https://developer.apple.com/documentation/xcode/previewing-localizations/
[23] - https://www.avanderlee.com/xcode/localization-testing-in-xcode/
[24] - https://developer.apple.com/videos/play/wwdc2022/10107/
[25] - https://novinfard.medium.com/make-your-ios-app-compatible-with-right-to-left-languages-in-swiftui-and-uikit-bdb164892ce3
[26] - https://appradar.com/blog/ios-localization-list-of-primary-secondary-languages
[27] - https://developer.apple.com/help/app-store-connect/manage-app-information/upload-app-previews-and-screenshots/
[28] - https://aso.dev/metadata/cross-localization/