JSON Dictionary - Lingo.dev CLI

What is JSON Dictionary?

JSON Dictionary is a localization format that stores all translations for multiple locales in a single JSON file. Each key contains an object with locale codes as keys and translated strings as values, making it easy to maintain all translations in one place.

For example:

{
  "navigation": {
    "en": "Home"
  },
  "buttons": {
    "submit": {
      "en": "Submit"
    },
    "cancel": {
      "en": "Cancel"
    }
  },
  "forms": {
    "login": {
      "username": {
        "en": "Username"
      }
    }
  }
}

What is Lingo.dev CLI?

Lingo.dev CLI is a free, open-source CLI for translating apps and content with AI. It's designed to replace traditional translation management software while integrating with existing pipelines.

To learn more, see Overview.

About this guide

This guide explains how to translate JSON dictionary files with Lingo.dev CLI.

You'll learn how to:

Create a project from scratch
Configure a translation pipeline
Generate translations with AI

Prerequisites

To use Lingo.dev CLI, ensure that Node.js v18+ is installed:

❯ node -v
v22.17.0

Step 1. Set up a project

In your project's directory, create an i18n.json file:

{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {}
}

This file defines the behavior of the translation pipeline, including what languages to translate between and where the localizable content exists on the file system.

To learn more about the available properties, see i18n.json.

Step 2. Configure the source locale

The source locale is the original language and region that your content was written in. To configure the source locale, set the locale.source property in the i18n.json file:

{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {}
}

The source locale must be provided as a BCP 47 language tag.

For the complete list of the locale codes that Lingo.dev CLI supports, see Supported locale codes.

Step 3. Configure the target locales

The target locales are the languages and regions you want to translate your content into. To configure the target locales, set the locale.targets property in the i18n.json file:

{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {}
}

Step 4. Create the source content

If you haven't already, create a JSON dictionary file that contains the content to be translated.

Note: During the translation process, the source content files will be overwritten to include the translated content (in addition to the source content).

Step 5. Create a bucket

In the i18n.json file, add a "json-dictionary" object to the buckets object:

{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {
    "json-dictionary": {}
  }
}

In the "json-dictionary" object, define an array of one or more include patterns:
```
{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {
    "json-dictionary": {
      "include": ["./example.json"]
    }
  }
}
```
These patterns define which files to translate and can either:
- point to specific file paths (e.g., "some/dir/file.json")
- use asterisks as wildcard placeholders (e.g., "some/dir/*.json")
Recursive glob patterns (e.g., **/*.json) are not supported.

Step 6. Configure an LLM

Lingo.dev CLI uses large language models (LLMs) to translate content with AI. To use one of these models, you need an API key from a supported provider.

To get up and running as quickly as possible, we recommend using Lingo.dev Engine — our own, hosted platform that offers 10,000 tokens of free, monthly usage:

Sign up for a Lingo.dev account.
Run the following command:
```
npx lingo.dev@latest login
```
This will open your default browser and ask you to authenticte.
Follow the prompts.

Step 7. Generate the translations

In the directory that contains the i18n.json file, run the following command:

npx lingo.dev@latest run

This command:

Reads the i18n.json file.
Finds the files that need to be translated.
Extracts the translatable content from the files.
Uses the configured LLM to translate the extracted content.
Writes the translated content back to the file system.

The first time translations are generated, an i18n.lock file is created. This file keeps track of what content has been translated, preventing unnecessary retranslations on subsequent runs.

Example

example.json (before translation)

{
  "navigation": {
    "en": "Home"
  },
  "buttons": {
    "submit": {
      "en": "Submit"
    },
    "cancel": {
      "en": "Cancel"
    }
  },
  "messages": {
    "welcome": {
      "en": "Welcome to our application"
    },
    "error": {
      "en": "An error occurred"
    }
  },
  "forms": {
    "login": {
      "title": {
        "en": "Login"
      },
      "fields": {
        "username": {
          "en": "Username"
        },
        "password": {
          "en": "Password"
        }
      }
    }
  }
}

example.json (after translation)

{
  "navigation": {
    "en": "Home",
    "es": "Inicio"
  },
  "buttons": {
    "submit": {
      "en": "Submit",
      "es": "Enviar"
    },
    "cancel": {
      "en": "Cancel",
      "es": "Cancelar"
    }
  },
  "messages": {
    "welcome": {
      "en": "Welcome to our application",
      "es": "Bienvenido a nuestra aplicación"
    },
    "error": {
      "en": "An error occurred",
      "es": "Ha ocurrido un error"
    }
  },
  "forms": {
    "login": {
      "title": {
        "en": "Login",
        "es": "Iniciar sesión"
      },
      "fields": {
        "username": {
          "en": "Username",
          "es": "Nombre de usuario"
        },
        "password": {
          "en": "Password",
          "es": "Contraseña"
        }
      }
    }
  }
}

i18n.json

{
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {
    "json-dictionary": {
      "include": ["./example.json"]
    }
  },
  "$schema": "https://lingo.dev/schema/i18n.json"
}

i18n.lock

version: 1
checksums:
  455da9346f4e772000927cd2ff5bb898:
    navigation: 104a3db3b671c04e167eafbe21e57881
    buttons/submit: 7c91ef5f747eea9f77a9c4f23e19fb2e
    buttons/cancel: 2e2a849c2223911717de8caa2c71bade
    messages/welcome: 1308168cca4fa5d8d7a0cf24e55e93fc
    messages/error: 53a2b5f5e7d83c737c8e02fe18fb4bdb
    forms/login/title: f4f219abeb5a465ecb1c7efaf50246de
    forms/login/fields/username: 2ee65bc2dd2f12cf2672f95b2a054bf8
    forms/login/fields/password: 223a61cf906ab9c40d22612c588dff48
  a8f80a1a4e0e0aa2750e514a8a6abacf:
    navigation: 104a3db3b671c04e167eafbe21e57881
    buttons/submit: 7c91ef5f747eea9f77a9c4f23e19fb2e
    buttons/cancel: 2e2a849c2223911717de8caa2c71bade
    messages/welcome: 1308168cca4fa5d8d7a0cf24e55e93fc
    messages/error: 53a2b5f5e7d83c737c8e02fe18fb4bdb
    forms/login/title: f4f219abeb5a465ecb1c7efaf50246de
    forms/login/fields/username: 2ee65bc2dd2f12cf2672f95b2a054bf8
    forms/login/fields/password: 223a61cf906ab9c40d22612c588dff48