YAML

AI translation for YAML files with Lingo.dev CLI

What is YAML?

YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files, data exchange, and structured data storage. It uses indentation to represent hierarchy and supports complex data structures.

For example:

title: "MyApp"
description: Hello, world!
welcome_message: 'Welcome to MyApp'

user_profile:
  display_name: "John Doe"
  bio: Software developer

navigation_items:
  - "Home"
  - "About"
  - "Contact"

product:
  name: "MyWidget"
  tagline: The best widget ever

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 YAML 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 one or more YAML files that contain the content to be translated. These files must be located at a path that includes the source locale somewhere in the path (e.g., as a directory name like en/ or as part of the filename like messages.en.yml).

Step 5. Create a bucket

  1. In the i18n.json file, add a "yaml" object to the buckets object:

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

  2. In the "yaml" 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": {
    "yaml": {
      "include": ["./[locale]/example.yml"]
    }
  }
}

    These patterns define which files to translate.

    The patterns themselves:

    • must contain [locale] as a placeholder for the configured locale
    • can point to file paths (e.g., "[locale]/config.yml")
    • can use asterisks as wildcard placeholders (e.g., "[locale]/*.yml")

    Recursive glob patterns (e.g., **/*.yml) 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:

  1. Sign up for a Lingo.dev account.

  2. Run the following command:

    npx lingo.dev@latest login

    This will open your default browser and ask you to authenticte.

  3. 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:

  1. Reads the i18n.json file.
  2. Finds the files that need to be translated.
  3. Extracts the translatable content from the files.
  4. Uses the configured LLM to translate the extracted content.
  5. 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

en/example.yml

title: "MyApp"
description: Hello, world!
welcome_message: 'Welcome to MyApp'

user_profile:
  display_name: "John Doe"
  bio: Software developer

navigation_items:
  - "Home"
  - "About"
  - "Contact"

product:
  name: "MyWidget"
  tagline: The best widget ever
  features:
    - "Easy to use"
    - "Fast and reliable"

settings:
  max_users: 100
  enabled: true
  timeout: 30.5

complex_structure:
  level_one:
    level_two:
      message: "Deep nested text"
locked_key_1: "This value is locked and should not be changed"
ignored_key_1: "This value is ignored and should not appear in target locales"

es/example.yml

title: "MyApp"
description: "¡Hola, mundo!"
welcome_message: "Bienvenido a MyApp"
user_profile:
  display_name: "Juan Pérez"
  bio: "Desarrollador de software"
navigation_items:
  - "Inicio"
  - "Acerca de"
  - "Contacto"
product:
  name: "MyWidget"
  tagline: "El mejor widget de todos"
  features:
    - "Fácil de usar"
    - "Rápido y confiable"
settings:
  max_users: 100
  enabled: true
  timeout: 30.5
complex_structure:
  level_one:
    level_two:
      message: "Texto anidado profundo"
locked_key_1: "This value is locked and should not be changed"

i18n.json

{
  "$schema": "https://lingo.dev/schema/i18n.json",
  "version": "1.10",
  "locale": {
    "source": "en",
    "targets": ["es"]
  },
  "buckets": {
    "yaml": {
      "include": ["./[locale]/example.yml"],
      "lockedKeys": ["locked_key_1"]
    }
  }
}

i18n.lock

version: 1
checksums:
  1b0d7c9f07dcc31a978bc337763270ea:
    title: 7dc70110429d46e3685f385bd2cc941c
    description: 0468579ef2fbc83c9d520c2f2f1c5059
    welcome_message: d1c3a9f35e377554a4ccaa467ca26614
    user_profile/display_name: febee8e9ab40b2fe5106d72675228d00
    user_profile/bio: 155ddcb7c93493ac72a37074eea0a653
    navigation_items/0: 104a3db3b671c04e167eafbe21e57881
    navigation_items/1: 944521eeeed2511833d2299931273c71
    navigation_items/2: 9afa39bc47019ee6dec6c74b6273967c
    product/name: ed21de171d538a49db999c47875f75a5
    product/tagline: b7ac41680e82d75ae7f5774f7ceef1b4
    product/features/0: c916ba887951a02793ff851853fd964f
    product/features/1: 1c60a04d6890c6ec910a7f2e6ec0ae7b
    complex_structure/level_one/level_two/message: b53034560bf657106e5aaea9160e357e