Translate a folder of JSON files containing translations into multiple languages.
Last updated 6 months ago by leolabs .
MIT · Repository · Bugs · Original npm · Tarball · package.json
$ cnpm install json-autotranslate 
SYNC missed versions from official npm registry.


This tool allows you to translate a locale folder containing multiple JSON files into multiple languages using Google Translate, DeepL, or manually. You can either use the translation keys (natural translation) or their values (key-based translation) as a source for translations.

If some of the strings have already been translated, they won't be translated again. This improves performance and ensures that you won't accidentally lose existing translations.

Interpolations (ICU: {name}, i18next: {{name}}, sprintf: %s) are replaced by placeholders (e.g. <0 />) before being passed to the translation service, so their structure doesn't get mangled by the translation.


$ yarn add json-autotranslate
# or
$ npm i -S json-autotranslate

Running json-autotranslate

$ yarn json-autotranslate
# or
$ npx json-autotranslate

Usage Examples

Translate natural language source files located in the locales directory using Google Translate and delete existing keys in translated JSON files that are no longer used.

$ yarn json-autotranslate -i locales -d -c service-account.json

Manually translate key-based source files located in the locales directory.

$ yarn json-autotranslate -i locales -s manual

Directory Structure

Your locales directory should look like this:

├── de
├── en
│   ├── login.json
│   └── register.json
├── fr
└── it

If you don't specify another source language, this tool will translate all files located in the en into all other languages that exist as directories. A single language directory (e.g. en) should only contain JSON files. Sub-directories and other files will be ignored.

File Structure

There are two ways that json-autotranslate can interpret files:

  • Natural Language (natural)
  • Key-Based (key-based)

If you don't specify a file structure type, json-autotranslate will automatically determine the type on a per-file basis. In most cases, this is sufficient.

Natural Language

This is the default way that this tool will interpret your source files. The keys will be used as the basis of translations. If one or more of the values in your source files don't match their respective key, you'll see a warning as this could indicate an inconsistency in your translations. You can fix those inconsistencies by passing the --fix-inconsistencies flag.

  "Your username doesn't exist.": "Your username doesn't exist.",
  "{email} is not a valid email address.": "{email} is not a valid email address."


If you pass the --key-based flag, this tool will use the source file's values as the basis of translations. Keys can be nested, the structure will be transfered over to the translated files as well.

  "ERRORS": {
    "USERNAME": "Your username doesn't exist.",
    "EMAIL": "{email} is not a valid email address."
  "LOGIN": "Login",
  "FORGOT_PASSWORD": "Forgot password?"

Available Services

As of this release, json-autotranslate offers four services:

  • google-translate (default, uses Google Translate to translate strings)
  • deepl (uses DeepL to translate strings)
  • manual (allows you to translate strings manually by entering them into the CLI)
  • dry-run (outputs a list of strings that will be translated without touching any files)

You can select a service using the -s or --service option. If you specify the --list-services flag, json-autotranslate will output a list of all available services.

Google Translate

To use this tool with Google Translate, you need to obtain valid credentials from Google. Follow these steps to get them:

  1. Select or create a Cloud Platform project
  2. Enable billing for your project (optional, I think)
  3. Enable the Google Cloud Translation API
  4. Set up authentication with a service account so you can access the API from your local workstation

You can specify the location of your downloaded JSON key file using the -c or --config option.


To use this tool with DeepL, you need to obtain an API key from their website. API keys are only available to DeepL Pro API users. If you don't have a Developer account yet, you can create one here.

DeepL charges a fixed monthly price plus a variable fee for every 500 translated characters.

After you have completed your sign-up, you can pass the API key to json-autotranslate using the -c or --config option.


This service doesn't require any configuration. You will be prompted to translate the source strings manually in the console.

Available Matchers

Matchers are used to replace interpolations with placeholders before they are sent to the translation service. This ensures that interpolations don't get scrambled in the process. As of this release, json-autotranslate offers four matchers for different styles of interpolation:

  • icu (default, matches ICU MessageFormat interpolations)
  • i18next (matches i18next interpolations)
  • sprintf (matches sprintf-style interpolations like %s)
  • none (doesn't match any interpolations)

You can select a matchers using the -m or --matcher option. If you specify the --list-matchers flag, json-autotranslate will output a list of all available matchers.

Available Options

  -i, --input <inputDir>               the directory containing language directories (default: ".")
  -l, --source-language <sourceLang>   specify the source language (default: "en")
  -t, --type <key-based|natural|auto>  specify the file structure type (default: "auto")
  -s, --service <service>              selects the service to be used for translation (default: "google-translate")
  --list-services                      outputs a list of available services
  -m, --matcher <matcher>              selects the matcher to be used for interpolations (default: "icu")
  --list-matchers                      outputs a list of available matchers
  -c, --config <value>                 supply a config parameter (e.g. path to key file) to the translation service
  -f, --fix-inconsistencies            automatically fixes inconsistent key-value pairs by setting the value to the key
  -d, --delete-unused-strings          deletes strings in translation files that don't exist in the template
  -h, --help                           output usage information


If you'd like to contribute to this project, please feel free to open a pull request.

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