Translate
Localizable.strings

Upload your .strings files, translate values while keeping format specifiers intact, and export back into the exact .lproj structure Xcode expects.

Translate .strings file
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en.lproj/Localizable.strings
/* Login screen */ "login.title" = "Sign In"; "login.button" = "Log In"; "home.welcome" = "Welcome, %@!";
/* Login screen */
"login.title" = "Sign In";
"login.button" = "Log In";
"home.welcome" = "Welcome, %@!";

Why teams use Localizable.strings
for translations

Each line pairs a key and a value with an equals sign, and every language gets its own file inside a language-specific .lproj folder, like en.lproj/Localizable.strings next to es.lproj/Localizable.strings. Xcode and the runtime pick the right folder automatically based on the user's language.

Placeholders follow printf-style specifiers: %@ for strings, %d for integers, and positional forms like %1$@ for reordering arguments across languages.

es.lproj/Localizable.strings
/* Login screen */ "login.title" = "Iniciar Sesión"; "login.button" = "Iniciar Sesión"; "home.welcome" = "¡Bienvenido, %@!";
/* Login screen */
"login.title" = "Iniciar Sesión";
"login.button" = "Iniciar Sesión";
"home.welcome" = "¡Bienvenido, %@!";
ViewController.swift
titleLabel.text = NSLocalizedString( "app.title", comment: "Application title" ) let itemsText = String.localizedStringWithFormat( NSLocalizedString("cart.items", comment: "Item count"), itemCount )
titleLabel.text = NSLocalizedString(
  "app.title",
  comment: "Application title"
)

let itemsText = String.localizedStringWithFormat(
  NSLocalizedString("cart.items", comment: "Item count"),
  itemCount
)

Setting up Localizable.strings in Xcode

In Xcode, add a new Strings file named Localizable, then localize it for each language you support under Project Settings → Info → Localizations. Xcode creates the matching .lproj folders automatically.

In code, load a value with the NSLocalizedString function, passing the key and an optional comment for translators. For strings with placeholders, use String.localizedStringWithFormat to insert dynamic values safely.

Beyond key and value

What SimpleLocalize keeps from your .strings files

One file per language

Each language sits in its own .lproj folder, matching what Xcode already expects on export.

Format specifiers protected

%@, %d and positional specifiers like %1$@ stay intact through auto-translation.

Universal placeholders

Convert %@, %d and %1$@ into a platform-independent {%s} / {%i} format for cross-platform export.

Pairs with .stringsdict

Plural and device-variant keys managed in .stringsdict line up with the same key here.

End-to-end workflow

Translate a Localizable.strings file end to end

Upload your English .strings file, run auto-translation across every language, and download one file per .lproj folder.

Terminal
simplelocalize upload \ --apiKey PROJECT_API_KEY \ --uploadFormat localizable-strings \ --uploadPath ./en.lproj/Localizable.strings
simplelocalize upload \
  --apiKey PROJECT_API_KEY \
  --uploadFormat localizable-strings \
  --uploadPath ./en.lproj/Localizable.strings

Upload your source .strings file

1
Push en.lproj/Localizable.strings to SimpleLocalize with the CLI. Block comments and key structure import as-is.
Translation editor
Key: home.welcome Source: Welcome, %@! Translated (es): ¡Bienvenido, %@! Key: order.summary Source: %1$@ ordered %2$d items for $%3$.2f Positional args reorder freely per language
Key: home.welcome
Source: Welcome, %@!
Translated (es): ¡Bienvenido, %@!

Key: order.summary
Source: %1$@ ordered %2$d items for $%3$.2f
Positional args reorder freely per language

Placeholders stay put during review

2
%@, %d and positional specifiers like %1$@ are highlighted in the editor, so a translator can move an argument without breaking the format string.
es.lproj/Localizable.strings (auto-translated)
"login.title" = "Iniciar Sesión"; "login.button" = "Iniciar Sesión";
"login.title" = "Iniciar Sesión";
"login.button" = "Iniciar Sesión";

Auto-translate every language

3
Run DeepL, Google Translate, OpenAI, Claude or Gemini across every target language, then review in the editor before anything is marked ready.
Terminal
simplelocalize download \ --apiKey PROJECT_API_KEY \ --downloadFormat localizable-strings \ --downloadPath ./{lang}.lproj/Localizable.strings
simplelocalize download \
  --apiKey PROJECT_API_KEY \
  --downloadFormat localizable-strings \
  --downloadPath ./{lang}.lproj/Localizable.strings

Download into every .lproj folder

4
Export lands as {lang}.lproj/Localizable.strings, or add UNIVERSAL_PLACEHOLDERS to convert specifiers back from the platform-independent format on the way out.

Migrating to Localizable.xcstrings

Apple's newer String Catalog format stores every language in one JSON-like file instead of separate .lproj files. Existing .strings files continue to work, and Xcode can migrate them to a String Catalog automatically whenever you are ready to move.

Both formats are supported on SimpleLocalize, so you can upload either one, or migrate at your own pace and switch which one you export.

Localizable.xcstrings (migrated)
{ "strings": { "login.title": { "localizations": { "en": { "stringUnit": { "value": "Sign In" } } } } } }
{
  "strings": {
    "login.title": {
      "localizations": {
        "en": { "stringUnit": { "value": "Sign In" } }
      }
    }
  }
}

Single file vs. many

One .xcstrings file replaces a separate .strings file per language.

Built-in pluralization

Native plural forms, no separate .stringsdict file required.

Device variants

Built-in support for device-specific translations, not possible in plain .strings.

Richer metadata

Extraction state and translation state travel with the file, not just the key and value.

For developers

A localization platform,
that keeps every platform in sync

SimpleLocalize gives your team a real editor and workflow around Localizable.strings, not just an import and export step.

Cross-platform placeholders

Convert native iOS placeholders into a platform-independent format, so the same string exports correctly to Android too.

Stays paired with .stringsdict

Plural and device-variant keys managed in .stringsdict line up with the same key here, edited as one string.

AI auto-translation

Translate new and changed strings with DeepL, Google Translate, OpenAI, Claude or Gemini.

CLI and REST API

Upload and download Localizable.strings files from the CLI, or automate the same logic through the REST API.

SimpleLocalize connects your code to professional translations

Best practices

Keeping Localizable.strings maintainable

Use descriptive keys

Clear, hierarchical keys that describe context and purpose age better than raw source text as a key.

Add meaningful comments

Pass a real comment to NSLocalizedString so translators get context, not just a bare string.

Use genstrings

Xcode's genstrings command-line tool extracts NSLocalizedString calls from your source automatically.

Test unsupported languages

Provide fallback text and verify your UI still works when a translation is missing.

Every Apple platform

Where Localizable.strings is used

Works with both Swift and Objective-C, across every Apple platform.

iOS

iOS

macOS

macOS

Swift

Swift

SwiftUI

SwiftUI

Objective-C

Objective-C

Xcode

Xcode

More conversions

Convert Localizable.strings to other formats

Free online converter, no account required. Upload a .strings file and download it in the format you need.

.strings to JSON

Move key-value pairs from an .lproj folder into JSON.

.strings to Android XML

Share the same source copy with your Android build.

.strings to String Catalog

Move key-value text into an Xcode String Catalog.

.strings to CSV

Hand a Localizable.strings file to a translator as a spreadsheet.

CTA FeaturesGo to Editor

Start translating Localizable.strings files

  • Format specifiers protected during auto-translation
  • Universal Placeholders for cross-platform exports
  • Auto-translation with DeepL, Google, OpenAI, Claude and Gemini
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Frequently asked questions about Localizable.strings

Is Localizable.strings deprecated?

It has been replaced by Apple's newer .xcstrings String Catalog format for new projects, but remains fully supported for existing UIKit and SwiftUI projects that haven't migrated.

Does this handle plurals too?

No, Localizable.strings holds simple key-value text only. Plural rules and device variants belong in a paired Localizable.stringsdict file.

Are placeholders like %@ preserved during translation?

Yes. Native iOS placeholders are protected during auto-translation, or can be converted to a platform-independent format with Universal Placeholders.

What does Universal Placeholders actually convert?

Native specifiers like %@, %d, %lld and positional forms like %1$@ convert to a curly-brace format such as {%s} or {%1$i}, which then converts back to the correct native format for whichever platform you export to.