Localization Reference

Complete API reference for iOS localization. Covers String Catalogs (.xcstrings), LocalizedStringResource, pluralization rules, RTL support, locale-aware formatting, and Xcode 26 type-safe localization.

When to Use This Reference

Use this reference when you need:

• String Catalog structure and configuration
• SwiftUI/UIKit localization patterns
• Pluralization for multiple languages
• RTL layout support (Arabic, Hebrew)
• Locale-aware date/number formatting
• Xcode 26 generated symbols and #bundle macro
• Migration from legacy .strings files

For quick patterns: Use String Catalogs for all new projects.

Example Prompts

Questions you can ask Claude that will draw from this reference:

• "How do I create and use a String Catalog?"
• "How do I handle pluralization in different languages?"
• "How do I support RTL layouts in SwiftUI?"
• "How do I use Xcode 26 type-safe localization symbols?"
• "How do I migrate from .strings to String Catalogs?"
• "How do I use LocalizedStringResource for deferred localization?"

What's Covered

String Catalogs (Xcode 15+)

• .xcstrings format and structure
• Automatic string extraction
• Plural variations
• Device-specific variations
• Translation state tracking

SwiftUI Localization

• Automatic Text view localization
• String(localized:comment:) pattern
• LocalizedStringResource for deferred resolution
• LocalizedStringKey usage

UIKit Localization

• NSLocalizedString patterns
• String(localized:) modern API (iOS 15+)
• Bundle-specific localization

Pluralization

• Language-specific plural rules
• String Catalog plural variations
• Format string patterns

RTL Support

• Leading/trailing vs left/right
• Layout mirroring
• Image flipping
• Testing RTL layouts

Xcode 26 Features

• Generated symbols (compile-time safety)
• Automatic comment generation
• #bundle macro for packages
• Refactoring tools

Key Pattern

SwiftUI Localization

// Automatic localization
Text("Welcome to WWDC!")

// With comment for translators
let title = String(localized: "Welcome to WWDC!",
                   comment: "Notification banner title")

// Deferred localization
struct CardView: View {
    let title: LocalizedStringResource
    var body: some View {
        Text(title)  // Resolved at render time
    }
}

Xcode 26 Type-Safe Symbols

// Generated symbols catch typos at compile time
Text(.appHomeScreenTitle)
Text(.subtitle(friendsPosts: 42))

// Swift Package localization
Text("My Collections", bundle: #bundle, comment: "Section title")

Documentation Scope

This page documents the axiom-localization reference skill—complete API coverage Claude uses when you need specific localization APIs, String Catalog patterns, or internationalization details.

For RTL testing: Use Xcode scheme → Right-to-Left Pseudolanguage.

Related

• hig — Typography and layout guidelines
• typography-ref — Font system reference

Resources

WWDC: 2025-225 (Xcode 26 localization), 2023-10155 (String Catalogs)

Docs: /xcode/localizing-and-varying-text-with-a-string-catalog, /foundation/localizedstringresource