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A small effort in making a plugin which helps you detect the users preferred language, as sent by the HTTP header.

Since version 2.0, this gem is Rack middleware.


  • Splits the http-header into languages specified by the user
  • Returns empty array if header is illformed.
  • Corrects case to xx-XX
  • Sorted by priority given, as much as possible.
  • Gives you the most important language
  • Gives compatible languages

See also:


When using in Rails:

class SomeController < ApplicationController

  def some_action

    http_accept_language.user_preferred_languages # => [ 'nl-NL', 'nl-BE', 'nl', 'en-US', 'en' ]
    available = %w{en en-US nl-BE}
    http_accept_language.preferred_language_from(available) # => 'nl-BE'

    http_accept_language.user_preferred_languages # => [ 'en-GB']
    available = %w{en-US}
    http_accept_language.compatible_language_from(available) # => 'en-US'



Older versions of Rails (pre 3.0) might need to include the middleware manually.

Usage in any Rack application, simple add the middleware:

require 'http_accept_language'
use HttpAcceptLanguage::Middleware
run YourAwesomeApp

Then you can access it:

class YourAwesomeApp

    available = %w(en en-US nl-BE)
    language = env.http_accept_language.preferred_language_from(available)
    [ 200, {}, ["Oh, you speak #{language}!"]]


Available methods

  • user_preferred_languages: Returns a sorted array based on user preference in HTTP_ACCEPT_LANGUAGE, sanitized and all.
  • preferred_language_from: Finds the locale specifically requested by the browser
  • compatible_language_from: Returns the first of the user_preferred_languages that is compatible with the available locales. Ignores region.
  • sanitize_available_locales: Returns a supplied list of available locals without any extra application info that may be attached to the locale for storage in the application.
  • language_region_compatible_from: Returns the first of the user preferred languages that is also found in available languages. Finds best fit by matching on primary language first and secondarily on region. If no matching region is found, return the first language in the group matching that primary language.


Without Bundler

Install the gem http_accept_language

With Bundler

Add the gem to your Gemfile:

gem 'http_accept_language'

Run bundle install to install it.

Released under the MIT license