What is a strings file in Xcode

Quick Summary

• Legacy format: .strings files are Xcode’s traditional localization format for simple key-value translations
• Language-specific: Each language requires a separate .strings file (e.g., en.strings, fr.strings)
• Simple structure: Plain text format with “key” = “value”; syntax
• Manual management: Developers must manually maintain and sync string files with code
• Limited features: Basic translations only – no built in pluralization or device variations
• Still supported: Works in all Xcode versions but largely superseded by String Catalogs

What is a .strings File?

A .strings file is Xcode’s traditional format for storing localized text in iOS apps. It’s a simple text file that maps string keys to their translated values using a straightforward “key” = “value”; syntax.

Each language in your app requires its own .strings file, typically named Localizable.strings and placed in language-specific folders like en.lproj for English or fr.lproj for French.

File Structure and Syntax

A typical .strings file looks like this:

/* Login screen title */
"login_title" = "Welcome Back";

/* Button text for signing in */
"sign_in_button" = "Sign In";

/* Error message for invalid credentials */
"invalid_credentials" = "Invalid username or password";

Key Components:

• Comments: Lines starting with /* provide context for translators
• Key: Unique identifier (usually in quotes)
• Value: Translated text for the current language
• Semicolon: Each entry must end with a semicolon

How to Use .strings Files

In your Swift code, reference strings using:

// iOS 15+ (String Catalogs preferred)
let title = String(localized: "login_title")

// Legacy approach (all iOS versions)
let title = NSLocalizedString("login_title", comment: "Login screen title")

At runtime, iOS automatically loads the appropriate .strings file based on the user’s language settings.

Limitations

.strings files work well for basic translations but have significant limitations:

• Manual synchronization: No automatic detection of new strings in code
• No pluralization: Cannot handle singular/plural variations (requires separate .stringsdict files)
• File proliferation: Multiple files per language become difficult to manage
• No state tracking: No built-in way to track translation progress
• Merge conflicts: Binary format can cause version control issues

For complex localization needs like pluralization, you’ll need to use .stringsdict files alongside your .strings files, which handle advanced formatting and plural rules.

File Organization

Traditional .strings file organization looks like this:

MyApp/
├── en.lproj/
│   └── Localizable.strings
├── fr.lproj/
│   └── Localizable.strings
├── es.lproj/
│   └── Localizable.strings
└── de.lproj/
    └── Localizable.strings

Each language folder contains identical file names with language specific translations.

Legacy vs Modern Approaches

Best Practices

While .strings files remain functional, Apple’s newer .xcstrings format is rapidly becoming the preferred standard for iOS and macOS localization.
The .xcstrings format offers better Xcode integration, improved collaboration features, and enhanced support for pluralization and device variants.
We recommend adopting .xcstrings to take advantage of modern tooling and align with Apple’s current development ecosystem.