No release in over a year
Export i18n translations and use them on JavaScript.



>= 0
>= 0.4.0
 Project Readme


Export i18n translations to JSON.
A perfect fit if you want to export translations to JavaScript.

Oh, you don't use Ruby? No problem! You can still use i18n-js
and the companion JavaScript package.

Tests Gem Gem MIT License


gem install i18n-js

Or add the following line to your project's Gemfile:

gem "i18n-js"

Create a default configuration file in ./config/i18n.yml

i18n init


About patterns:

  • Patterns can use * as a wildcard and can appear more than once.
    • * will include everything
    • *.messages.*
  • Patterns starting with ! are excluded.
    • !*.activerecord.* will exclude all ActiveRecord translations.
  • You can use groups:
    • {pt-BR,en}.js.* will include only pt-BR and en translations, even if more languages are available.


Patterns use glob, so check it out for the most up-to-date documentation about what's available.

The config file:

  - file: app/frontend/locales/en.json
      - "*"
      - "!*.activerecord"
      - "!*.errors"
      - "!*.number.nth"

  - file: app/frontend/locales/:locale.:digest.json
      - "*"

The output path can use the following placeholders:

  • :locale - the language that's being exported.
  • :digest - the MD5 hex digest of the exported file.

The example above could generate a file named app/frontend/locales/en.7bdc958e33231eafb96b81e3d108eff3.json.

The config file is processed as erb, so you can have dynamic content on it if you want. The following example shows how to use groups from a variable.

<% group = "{en,pt}" %>

  - file: app/frontend/translations.json
      - "<%= group %>.*"
      - "!<%= group %>.activerecord"
      - "!<%= group %>.errors"
      - "!<%= group %>.number.nth"

Exporting locale.yml to locale.json

Your i18n yaml file can be exported to JSON using the Ruby API or the command line utility. Examples of both approaches are provided below:

The Ruby API:

require "i18n-js"

# The following call performs the same task as the CLI `i18n export` command "config/i18n.yml")

# You can provide the config directly using the following
config = {
    {"file"=>"app/javascript/locales/:locale.json", "patterns"=>["*"]}
} config)
#=> ["app/javascript/locales/de.json", "app/javascript/locales/en.json"]


$ i18n --help


- init: Initialize a project
- export: Export translations as JSON files
- version: Show package version
- plugins: List plugins that will be activated
- lint:translations: Check for missing translations
- lint:scripts: Lint files using TypeScript

Run `i18n COMMAND --help` for more information on specific commands.

By default, i18n will use config/i18n.yml and config/environment.rb as the configuration files. If you don't have these files, then you'll need to specify both --config and --require.


Built-in plugins:


Embed fallback translations inferred from the default locale. This can be useful in cases where you have multiple large translation files and don't want to load the default locale together with the target locale.

To use it, add the following to your configuration file:

  enabled: true

By default, i18n-js will export only JSON files out of your translations. This plugin allows exporting other file formats. To use it, add the following to your configuration file:

  enabled: true
    - template: path/to/template.erb
      output: "%{dir}/%{base_name}.ts"

You can export multiple files by defining more entries.

The output name can use the following placeholders:

  • %{dir}: the directory where the translation file is.
  • %{name}: file name with extension.
  • %{base_name}: file name without extension.
  • %{digest}: MD5 hexdigest from the generated file.

The template file must be a valid eRB template. You can execute arbitrary Ruby code, so be careful. An example of how you can generate a file can be seen below:

/* eslint-disable */
<%= banner %>

import { i18n } from "config/i18n";<%= JSON.pretty_generate(translations) %>);

This template is loading the instance from config/i18n and storing the translations that have been loaded. The banner(comment: "// ", include_time: true) method is built-in. The generated file will look something like this:

/* eslint-disable */
// File generated by i18n-js on 2022-12-10 15:37:00 +0000

import { i18n } from "config/i18n";{
  en: {
    "bunny rabbit adventure": "bunny rabbit adventure",
    "hello sunshine!": "hello sunshine!",
    "time for bed!": "time for bed!",
  es: {
    "bunny rabbit adventure": "conejito conejo aventura",
    bye: "adios",
    "time for bed!": "hora de acostarse!",
  pt: {
    "bunny rabbit adventure": "a aventura da coelhinha",
    bye: "tchau",
    "time for bed!": "hora de dormir!",

Plugin API

You can transform the exported translations by adding plugins. A plugin must inherit from I18nJS::Plugin and can have 4 class methods (they're all optional and will default to a noop implementation). For real examples, see lib/i18n-js/embed_fallback_translations_plugin.rb and lib/i18n-js/export_files_plugin.rb

# frozen_string_literal: true

module I18nJS
  class SamplePlugin < I18nJS::Plugin
    # This method is responsible for transforming the translations. The
    # translations you'll receive may be already be filtered by other plugins
    # and by the default filtering itself. If you need to access the original
    # translations, use `I18nJS.translations`.
    def transform(translations:)
      # transform `translations` here…


    # In case your plugin accepts configuration, this is where you must validate
    # the configuration, making sure only valid keys and type is provided.
    # If the configuration contains invalid data, then you must raise an
    # exception using something like
    # `raise I18nJS::Schema::InvalidError, error_message`.
    # Notice the validation will only happen when the plugin configuration is
    # set (i.e. the configuration contains your config key).
    def validate_schema
      # validate plugin schema here…

    # This method must set up the basic plugin configuration, like adding the
    # config's root key in case your plugin accepts configuration (defined via
    # the config file).
    # If you don't add this key, the linter will prevent non-default keys from
    # being added to the configuration file.
    def setup
      # If you plugin has configuration, uncomment the line below
      # I18nJS::Schema.root_keys << config_key

    # This method is called whenever `**kwargs)` finishes exporting
    # JSON files based on your configuration.
    # You can use it to further process exported files, or generate new files
    # based on the translations that have been exported.
    def after_export(files:)
      # process exported files here…

The class I18nJS::Plugin implements some helper methods that you can use:

  • I18nJS::Plugin#config_key: the configuration key that was inferred out of your plugin's class name.
  • I18nJS::Plugin#config: the plugin configuration.
  • I18nJS::Plugin#enabled?: whether the plugin is enabled or not based on the plugin's configuration.

To distribute this plugin, you need to create a gem package that matches the pattern i18n-js/*_plugin.rb. You can test whether your plugin will be found by installing your gem, opening a iRB session and running Gem.find_files("i18n-js/*_plugin.rb"). If your plugin is not listed, then you need to double check your gem load path and see why the file is not being loaded.

Listing missing translations

To list missing and extraneous translations, you can use i18n lint:translations. This command will load your translations similarly to how i18n export does, but will output the list of keys that don't have a matching translation against the default locale. Here's an example:

$ i18n lint:translations
=> Config file: "./config/i18n.yml"
=> Require file: "./config/environment.rb"
=> Check "./config/i18n.yml" for ignored keys.
=> en: 232 translations
=> pt-BR: 5 missing, 1 extraneous, 1 ignored
   - pt-BR.actors.github.metrics (missing)
   - pt-BR.actors.github.metrics_hint (missing)
   - pt-BR.actors.github.repo_metrics (missing)
   - pt-BR.actors.github.repository (missing)
   - pt-BR.actors.github.user_metrics (missing)
   - pt-BR.github.repository (extraneous)

This command will exit with status 1 whenever there are missing translations. This way you can use it as a CI linting tool.

You can ignore keys by adding a list to the config file:

  - file: app/frontend/locales/en.json
      - "*"
      - "!*.activerecord"
      - "!*.errors"
      - "!*.number.nth"

  - file: app/frontend/locales/:locale.:digest.json
      - "*"

    - en.mailer.login.subject
    - en.mailer.login.body


In order to avoid mistakenly ignoring keys, this configuration option only accepts the full translation scope, rather than accepting a pattern like pt.ignored.scope.*.

Linting your JavaScript/TypeScript files

To lint your script files and check for missing translations (which can signal that you're either using wrong scopes or forgot to add the translation), use i18n lint:scripts. This command will parse your JavaScript/TypeScript files and extract all scopes being used. This command requires a Node.js runtime. You can either specify one via --node-path, or let the plugin infer a binary from your $PATH.

The comparison will be made against the export JSON files, which means it'll consider transformations performed by plugins (e.g. the output files may be affected by embed_fallback_translations plugin).

The translations that will be extract must be called as one of the following ways:

  • i18n.t(scope, options)
  • i18n.translate(scope, options)
  • t(scope, options)

Notice that only literal strings can be used, as in i18n.t("message"). If you're using dynamic scoping through variables (e.g. const scope = "message"; i18n.t(scope)), they will be skipped.

$ i18n lint:scripts
=> Config file: "./config/i18n.yml"
=> Require file: "./config/environment.rb"
=> Node: "/Users/fnando/.asdf/shims/node"
=> Available locales: [:en, :es, :pt]
=> Patterns: ["!(node_modules)/**/*.js", "!(node_modules)/**/*.ts", "!(node_modules)/**/*.jsx", "!(node_modules)/**/*.tsx"]
=> 9 translations, 11 missing, 4 ignored
   - test/scripts/lint/file.js:1:1: en.js.missing
   - test/scripts/lint/file.js:1:1: es.js.missing
   - test/scripts/lint/file.js:1:1: pt.js.missing
   - test/scripts/lint/file.js:2:8: en.base.js.missing
   - test/scripts/lint/file.js:2:8: es.base.js.missing
   - test/scripts/lint/file.js:2:8: pt.base.js.missing
   - test/scripts/lint/file.js:4:8: en.js.missing
   - test/scripts/lint/file.js:4:8: es.js.missing
   - test/scripts/lint/file.js:4:8: pt.js.missing
   - test/scripts/lint/file.js:6:1: en.another_ignore_scope
   - test/scripts/lint/file.js:6:1: es.another_ignore_scope

This command will list all locales and their missing translations. To avoid listing a particular translation, you can set lint_scripts.ignore or lint_translations.ignore in your config file.

  - file: app/frontend/translations.json
      - "*"

    - ignore_scope # will ignore this scope on all languages
    - pt.another_ignore_scope # will ignore this scope only on `pt`

You can also set the patterns that will be looked up. By default, it scans all JavaScript and TypeScript files that don't live on node_modules.

  - file: app/frontend/translations.json
      - "*"

    - "app/assets/**/*.ts"

Automatically export translations

Using watchman

Create a script at bin/i18n-watch.

#!/usr/bin/env bash


watchman watch-del "$root"
watchman watch-project "$root"
watchman trigger-del "$root" i18n

watchman -j <<-JSON
    "name": "i18n",
    "expression": [
      ["match", "config/locales/**/*.yml", "wholename"],
      ["match", "config/i18n.yml", "wholename"]
    "command": ["i18n", "export"]

# If you're running this through Foreman,
# then uncomment the following lines:
# while true; do
#   sleep 1
# done

Make it executable with chmod +x bin/i18n-watch. To watch for changes, run ./bin/i18n-watch. If you're using Foreman, make sure you uncommented the lines that keep the process running (while..), and add something like the following line to your Procfile:

i18n: ./bin/i18n-watch

Using guard

Install guard and guard-compat. Then create a Guardfile with the following configuration:

      run_on_start: true,
      config_file: "./config/i18n.yml",
      require_file: "./config/environment.rb") do

If your files are located in a different path, remember to configure file paths accordingly.

Now you can run guard start -i.

Using listen

Create a file under config/initializers/i18n.rb with the following content:

Rails.application.config.after_initialize do
  require "i18n-js/listen"

The code above will watch for changes based on config/i18n.yml and config/locales. You can customize these options:

  • config_file - i18n-js configuration file
  • locales_dir - one or multiple directories to watch for locales changes
  • options - passed directly to listen
  • run_on_start - export files on start. Defaults to true. When disabled, files will be exported only when there are file changes.


  config_file: "config/i18n.yml",
  locales_dir: ["config/locales", "app/views"],
  options: {only: %r{.yml$}},
  run_on_start: false

Integrating with your frontend

You're done exporting files, now what? Well, go to i18n to discover how to use the NPM package that loads all the exported translation.


I'm running v3. Is there a migration plan?

There's a document outlining some of the things you need to do to migrate from v3 to v4. It may not be as complete as we'd like it to be, so let us know if you face any issues during the migration that is not outlined in that document.

How can I export translations without having a database around?

Some people may have a build process using something like Docker that don't necessarily have a database available. In this case, you may define your own loading file by using something like i18n export --require ./config/i18n_export.rb, where i18n_export.rb may look like this:

# frozen_string_literal: true

require "bundler/setup"
require "rails"
require "active_support/railtie"
require "action_view/railtie"

I18n.load_path += Dir["./config/locales/**/*.yml"]


You may not need to load the ActiveSupport and ActionView lines, or you may need to add additional requires for other libs. With this approach you have full control on what's going to be loaded.




For more details about how to contribute, please read


The gem is available as open source under the terms of the MIT License. A copy of the license can be found at

Code of Conduct

Everyone interacting in the i18n-js project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.