R18n is an i18n tool to translate your Ruby application into several languages.

Use r18n-rails or sinatra-r18n to localize Web applications and r18n-desktop to localize desktop application.


  • Nice Ruby-style syntax.
  • Filters.
  • Model Translation (or any Ruby object).
  • Autodetect user locales.
  • Flexible locales.
  • Total flexibility.

See full features in main README.


To add i18n support to your app, you can use the particular plugin for your environment: r18n-rails, sinatra-r18n or r18n-desktop.

If you develop you own plugin or want to use only core gem, you will need to set default translation places and current locale:

R18n.default_places = 'path/to/translations'

You can use R18n.t to get translations and R18n.l to localize times and numbers. But more useful is to add helpers to fast access the R18n:

include R18n::Helpers

t.yes              #=> "Yes"
l Time.now, :human #=> "now"

r18n.locale.code   #=> "en"

To set locale only for current thread use R18n.thread_set.


Translation files are in YAML format by default and have names like en.yml (English) or en-us.yml (USA English dialect) with language/country code (RFC 3066).

In your translation files you can use:

  • Strings

    robot: This is a robot
    percent: "Percent sign (%)"
  • Numbers

    number: 123
    float: 12.45
  • Pluralizable messages

    robots: !!pl
      0: No robots
      1: One robot
      n: %1 robots
  • Filters

    filtered: !!custom_type
      This content will be processed by a filter

To get the translated string use a method with the key name or square brackets [] for keys, which is the same with Object methods (class, inspect, etc):

t.robot    #=> "This is a robot"
t[:robot]  #=> "This is a robot"

Translation may be hierarchical:

t.post.add     #=> "Add post"
t[:post][:add] #=> "Add post"

If the locale isn’t found in the user’s requested locale, R18n will search for it in sublocales or in another locale, which the user also can accept:

t.not.in.english #=> "В английском нет"

The translated string has a locale method for determining its locale (Locale instance or code string if locale is’t supported in R18n):

i18n.not.in.english.locale #=> Locale ru (Русский)

You can include parameters in the translated string by specifying arguments:

name: My name is %1
t.name('John') #=> "My name is John"

Pluralizable messages get their item count from the first argument:

t.robots(0)  #=> "No robots"
t.robots(1)  #=> "One robot"
t.robots(50) #=> "50 robots"

If there isn’t a pluralization for a particular number, translation will be use n. If there isn’t a locale file for translation, it will use the English pluralization rule (0, 1 and n).

You can check if the key has a translation:

t.post.add.translated?   #=> true
t.not.exists.translated? #=> false

You can set a default value for untranslated strings:

t.not.exists | 'default' #=> "default"

You can query the translation keys:

t.counties.translation_keys.each do |county|
  puts t.counties[county]

R18n already has translations for common words for most built in locales. See base/ the source.

t.yes    #=> "Yes"
t.cancel #=> "Cancel"
t.delete #=> "Delete"


You can also add you own filters for translations: escape HTML entities, convert from Markdown syntax, etc. Filters can be passive, only being processed when loaded.

friendship: !!gender
  f: She adds a friend
  m: He adds a friend
R18n::Filters.add('gender', :user_gender) do |content, config, user|
  if user.female?

t.friendship(anne) #=> "She adds a friend"

To create a filter you pass the following to R18n::Filters.add:

  • Filter target. YAML type (!!type), String for all translations of R18n::Untranslated for missing translations.
  • Optional filter name, to disable, enable or delete it later by R18n::Filters.off, R18n::Filters.on and R18n::Filters.delete.
  • Hash with options:
    • :passive => true to filter translations only on load;
    • :position within the list of current filters of this type (by default a new filter will be inserted into last position).

The filter will receive at least two arguments:

  • Translation (possibly already filtered by other filters for this type earlier in the list).
  • A Hash with translation locale and path.
  • Parameters from translation request will be in the remaining arguments.

In Rails application put your filters to app/i18n/filters.rb, it will be automatically reloaded in development.

HTML Escape

R18n contains 2 filters to escape HTML entities: by YAML type and global. If you need to escape HTML in some translations, just set !!escape YAML type:

greater: !!escape
  1 < 2 is true
t.greater #=> "1 &lt; 2 is true"

If you develop web application and want to escape HTML in all translations, just activate the global escape filter:


If you enable global HTML escape, you may still use !!html YAML type to disable escaping on some values:

warning: !!html
t.warning #=> "<b>Warning</b>"


To use Markdown in your translations you must install the Kramdown gem:

hi: !!markdown
  **Hi**, people!
t.hi #=> "<p><strong>Hi</strong>, people!</p>"

If you can’t use Kramdown you can redefine Markdown filter to use your own parser:

# Disable standard Markdown filter
# Add new filter for !!markdown YAML type
Filters.add('markdown', :passive => true) do |content, config|
  require 'redcarpet'
  markdown = ::Redcarpet::Markdown.new(Redcarpet::Render::HTML)


To use Textile in your translations you must install the RedCloth gem:

alarm: !!textile
  It will delete _all_ users!
t.alarm #=> "<p>It will delete <em>all</em> users!</p>"


You can use lambdas in your translations.

sum: !!proc |x, y| x + y
t.sum(1, 2) #=> 3

If this is unsafe in your application (for example, user can change translations), you can disable it:



You can print numbers and floats according to the rules of the user locale:

l -12000.5 #=> "−12,000.5"

Number and float formatters will also put real typographic minus and put non-breakable thin spaces (for locale, which use it as digit separator).

You can translate months and week day names in Time, Date and DateTime by the strftime method:

l Time.now, '%B'  #=> "September"

R18n has some built-in time formats for locales: :human, :full and :standard (the default):

l Time.now, :human #=> "now"
l Time.now, :full  #=> "August 9th, 2009 21:47"
l Time.now         #=> "08/09/2009 21:41"
l Time.now.to_date #=> "08/09/2009"


You can add i18n support to any classes, including ORM models (ActiveRecord, DataMapper, MongoMapper, Mongoid or others):

class Product
  include DataMapper::Resource
  property :title_ru, String
  property :title_en, String

  include R18n::Translated
  translations :title

# For example, user only knows Russian

# Set English (default) title
product.title_en = "Anthrax"
product.title #=> "Anthrax"

# Set value for user locale (Russian)
product.title = "Сибирская язва"
product.title #=> "Сибирская язва"

product.title_en #=> "Anthrax"
product.title_ru #=> "Сибирская язва"

See R18n::Translated for documentation.


All supported locales are stored in R18n gem in locales directory. If you want to add your locale, please fork this project and send a pull request or email me at andrey@sitnik.ru.

To get information about a locale create an R18n::Locale instance:

locale = R18n.locale('en')

You can then get the following from the locale:

  • Locale title and RFC 3066 code:

    locale.title #=> "English"
    locale.code  #=> "en"
  • Language direction (left to right, or right to left for Arabic and Hebrew):

    locale.ltr? #=> true
  • Week start day (:monday or :sunday):

    locale.week_start #=> :sunday


You can load translations from anywhere, not just from YAML files. To load translation you must create loader class with 2 methods:

  • available – return array of locales of available translations;
  • load(locale) – return Hash of translation.

Pass its instance to R18n.default_places or R18n.set(locales, loaders)

R18n.default_places = MyLoader.new(loader_param)

You can set your default loader and pass it to R18n.set as the only constructor argument:

R18n.default_loader = MyLoader
R18n.default_places = loader_param

R18n.set('en', different_loader_param)

If you want to load a translation with some type for filter, use R18n::Typed struct:

# Loader will return something like:
{ 'users' => R18n::Typed.new('pl', { 1 => '1 user', 'n' => '%1 users' }) }

# To use pluralization filter ("pl" type):
t.users(5) #=> "5 users"

You can also set several loaders to merge translations from different sources:

R18n.default_places = [MyLoader.new, DBLoader.new, 'path/to/yaml']

Extension Translations

For r18n plugin you can add loaders with translations, which will be used with application translations. For example, DB plugin may place translations for error messages in extension directory. R18n contain translations for base words as extension directory too.

R18n.extension_places << R18n::Loader::YAML.new('./error_messages/')

Add Locale

If R18n hasn’t got locale file for your language, please add it. It’s very simple:

  • Create the file code.rb in the locales/ directory for your language and describe locale. Just copy from another locale and change the values.
    • If your country has alternate languages (for example, in exUSSR countries most people also know Russian), add sublocales %w{another_locale en}.
  • Create in base/ file code.yml for your language and translate the base messages. Just copy file from language, which you know, and rewrite values.
  • If your language needs some special logic (for example, different pluralization or time formatters) you can extend R18n::Locale class methods.
  • Send a pull request via GitHub http://github.com/ai/r18n or just write email with the files to me andrey@sitnik.ru.

Code is RFC 3066 code for your language (for example, “en” for English and “fr-CA” for Canadian French). Email me with any questions you may have, you will find other contact addresses at http://sitnik.ru.


R18n is licensed under the GNU Lesser General Public License version 3. See the LICENSE file or http://www.gnu.org/licenses/lgpl.html.


Andrey “A.I.” Sitnik andrey@sitnik.ru