Convert String Catalog to Extension JSON online
Upload a Xcode String Catalog (.xcstrings) file and download it as Browser extension messages.json. Translation keys, plurals and placeholders are preserved. Free, no account needed.
Pick the source format or let the converter detect it from the file.
Choose the format you want to download.
The _locales/xx/messages.json format used by Chrome, Firefox and Edge extensions. Every key holds a message and an optional description for translators.
Need it the other way round? Convert Extension JSON to String Catalog.
From: Xcode String Catalog (.xcstrings)
String Catalogs were introduced in Xcode 15 and store all languages, plural variants and device variations of a project in one JSON-based .xcstrings file.
Used by: Xcode 15+, SwiftUI, iOS 17+. All languages in one file. Read the String Catalog format guide.
{
"sourceLanguage" : "en",
"strings" : {
"hello world" : {
"comment" : "My Hello World description",
"extractionState" : "manual",
"localizations" : {
"pl" : {
"stringUnit" : {
"state" : "translated",
"value" : "Witaj Świecie!"
}
}
}
}
},
"version" : "1.0"
}To: Browser extension messages.json
The _locales/xx/messages.json format used by Chrome, Firefox and Edge extensions. Every key holds a message and an optional description for translators.
Used by: Chrome extensions, Firefox add-ons, Edge extensions. One language per file. Read the Extension JSON format guide.
{
"appName": {
"message": "My Extension",
"description": "The name of the extension"
},
"greeting": {
"message": "Hello, $USER$!",
"description": "Greets the user",
"placeholders": {
"user": {
"content": "$1",
"example": "John"
}
}
}
}How to convert String Catalog to Extension JSON
- Drop your .xcstrings file into the converter above, or paste its content.
- Click Convert. You get one .json file per language.
- Preview the result, copy it or download the files.
What changes between String Catalog and Extension JSON
- String Catalog holds every language in one file, so the converter writes one Extension JSON file per language found in the source.
Convert and translate in one place
If you need the Extension JSON file in more languages, the fastest route is a free SimpleLocalize project: import the String Catalog file, add languages, run auto-translation with DeepL, Google Translate, OpenAI, Claude or Gemini, and download the result as Extension JSON. The CLI does the same from CI with upload and download commands, so the conversion becomes part of your build. See also translating String Catalog files.
Frequently asked questions
Is the converter free?
Yes. There is no signup and no limit on the number of conversions beyond a few requests per second.
Are my files stored?
No. The file is parsed in memory, converted and returned in the same request. Nothing is written to disk or a database.
What about plurals and placeholders?
Plural forms are normalized to ICU message syntax and written back in the native form of Extension JSON. Placeholders are kept, and Apple and Android specific syntax is translated between platforms. Read more in the pluralization guide.
Convert String Catalog to other formats
Translate your Extension JSON files
- Import String Catalog or Extension JSON files into a free project
- Auto-translate with DeepL, Google, OpenAI, Claude or Gemini
- Download in any of the supported formats or publish to the CDN