diff --git a/app/assets/javascripts/admin/components/site-setting.js.es6 b/app/assets/javascripts/admin/components/site-setting.js.es6
index d796e274921..73e8160a28c 100644
--- a/app/assets/javascripts/admin/components/site-setting.js.es6
+++ b/app/assets/javascripts/admin/components/site-setting.js.es6
@@ -64,16 +64,16 @@ export default Ember.Component.extend(BufferedContent, {
   }.on("willDestroyElement"),
 
   _save() {
-    const self = this,
-          setting = this.get('buffered');
-    SiteSetting.update(setting.get('setting'), setting.get('value')).then(function() {
-      self.set('validationMessage', null);
-      self.commitBuffer();
-    }).catch(function(e) {
+    const setting = this.get('buffered'),
+      action = SiteSetting.update(setting.get('setting'), setting.get('value'));
+    action.then(() => {
+      this.set('validationMessage', null);
+      this.commitBuffer();
+    }).catch((e) => {
       if (e.jqXHR.responseJSON && e.jqXHR.responseJSON.errors) {
-        self.set('validationMessage', e.jqXHR.responseJSON.errors[0]);
+        this.set('validationMessage', e.jqXHR.responseJSON.errors[0]);
       } else {
-        self.set('validationMessage', I18n.t('generic_error'));
+        this.set('validationMessage', I18n.t('generic_error'));
       }
     });
   },
diff --git a/app/assets/javascripts/admin/models/site-setting.js.es6 b/app/assets/javascripts/admin/models/site-setting.js.es6
index 51037626634..6ed78787968 100644
--- a/app/assets/javascripts/admin/models/site-setting.js.es6
+++ b/app/assets/javascripts/admin/models/site-setting.js.es6
@@ -48,7 +48,7 @@ SiteSetting.reopenClass({
   update(key, value) {
     const data = {};
     data[key] = value;
-    return ajax("/admin/site_settings/" + key, { type: 'PUT', data });
+    return ajax(`/admin/site_settings/${key}`, { type: 'PUT', data });
   }
 });
 
diff --git a/app/controllers/admin/site_settings_controller.rb b/app/controllers/admin/site_settings_controller.rb
index 87478597a17..ed64aa2d4bb 100644
--- a/app/controllers/admin/site_settings_controller.rb
+++ b/app/controllers/admin/site_settings_controller.rb
@@ -1,4 +1,7 @@
 class Admin::SiteSettingsController < Admin::AdminController
+  rescue_from Discourse::InvalidParameters do |e|
+    render_json_error e.message, status: 422
+  end
 
   def index
     render_json_dump(site_settings: SiteSetting.all_settings, diags: SiteSetting.diags)
@@ -9,15 +12,17 @@ class Admin::SiteSettingsController < Admin::AdminController
     id = params[:id]
     value = params[id]
     value.strip! if value.is_a?(String)
-    begin
-      # note, as of Ruby 2.3 symbols are GC'd so this is considered safe
-      if SiteSetting.hidden_settings.include?(id.to_sym)
-        raise Discourse::InvalidParameters, "You are not allowed to change hidden settings"
-      end
-      SiteSetting.set_and_log(id, value, current_user)
-      render nothing: true
-    rescue Discourse::InvalidParameters => e
-      render json: { errors: [e.message] }, status: 422
+    raise_access_hidden_setting(id)
+    SiteSetting.set_and_log(id, value, current_user)
+    render nothing: true
+  end
+
+  private
+
+  def raise_access_hidden_setting(id)
+    # note, as of Ruby 2.3 symbols are GC'd so this is considered safe
+    if SiteSetting.hidden_settings.include?(id.to_sym)
+      raise Discourse::InvalidParameters, "You are not allowed to change hidden settings"
     end
   end
 
diff --git a/app/models/site_setting.rb b/app/models/site_setting.rb
index 2e4fa838f34..4159a1cfb5b 100644
--- a/app/models/site_setting.rb
+++ b/app/models/site_setting.rb
@@ -14,11 +14,7 @@ class SiteSetting < ActiveRecord::Base
 
   def self.load_settings(file)
     SiteSettings::YamlLoader.new(file).load do |category, name, default, opts|
-      if opts.delete(:client)
-        client_setting(name, default, opts.merge(category: category))
-      else
-        setting(name, default, opts.merge(category: category))
-      end
+      setting(name, default, opts.merge(category: category))
     end
   end
 
@@ -31,6 +27,11 @@ class SiteSetting < ActiveRecord::Base
     end
   end
 
+  # `current` hash is not populated everytime when load a site setting
+  # in order to support locale default. Instead, we simply `refresh!` once.
+  # This should only affects the spec in which you should populate `current`
+  refresh!
+
   client_settings << :available_locales
 
   def self.available_locales
diff --git a/config/environments/development.rb b/config/environments/development.rb
index d9c10db2e8a..dc0a0cda2e7 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -59,6 +59,9 @@ Discourse::Application.configure do
   end
 
   config.after_initialize do
+    SiteSetting.defaults.set_regardless_of_locale(:port, 3000)
+    SiteSetting.refresh!
+
     if ENV['BULLET']
       Bullet.enable = true
       Bullet.rails_logger = true
diff --git a/config/environments/test.rb b/config/environments/test.rb
index 5cd785ce22c..c2129f70953 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -46,4 +46,22 @@ Discourse::Application.configure do
     config.logger = Logger.new(nil)
     config.log_level = :fatal
   end
+
+  config.after_initialize do
+    SiteSetting.defaults.tap do |s|
+      s.set_regardless_of_locale(:s3_upload_bucket, 'bucket')
+      s.set_regardless_of_locale(:min_post_length, 5)
+      s.set_regardless_of_locale(:min_first_post_length, 5)
+      s.set_regardless_of_locale(:min_private_message_post_length, 10)
+      s.set_regardless_of_locale(:crawl_images, false)
+      s.set_regardless_of_locale(:download_remote_images_to_local, false)
+      s.set_regardless_of_locale(:unique_posts_mins, 0)
+      s.set_regardless_of_locale(:queue_jobs, false)
+      # disable plugins
+      if ENV['LOAD_PLUGINS'] == '1'
+        s.set_regardless_of_locale(:discourse_narrative_bot_enabled, false)
+      end
+    end
+    SiteSetting.refresh!
+  end
 end
diff --git a/config/site_settings.yml b/config/site_settings.yml
index b9092e186cf..3f85d1e1aa1 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -12,6 +12,9 @@
 # shadowed_by_global - "Shadow" a site setting with a GlobalSetting. If the GlobalSetting
 #                      exists it will be used instead of the setting and the setting will be hidden.
 #                      Useful for things like API keys on multisite.
+# locale_default     - A hash which overrides according to `SiteSetting.default_locale`.
+#                      The key should be as the same as possible value of default_locale.
+#
 #
 # type: email    - Must be a valid email address.
 # type: username - Must match the username of an existing user.
@@ -68,11 +71,6 @@ required:
     default: ''
 
 basic:
-  default_locale:
-    default: 'en'
-    enum: 'LocaleSiteSetting'
-    refresh: true
-    shadowed_by_global: true
   allow_user_locale:
     client: true
     default: false
@@ -432,21 +430,24 @@ posting:
   min_post_length:
     client: true
     min: 1
-    default:
-      test: 5
-      default: 20
+    default: 20
+    locale_default:
+      zh_CN: 8
+      zh_TW: 8
   min_first_post_length:
     client: true
     min: 1
-    default:
-      test: 5
-      default: 20
+    default: 20
+    locale_default:
+      zh_CN: 8
+      zh_TW: 8
   min_private_message_post_length:
     client: true
     min: 1
-    default:
-      test: 5
-      default: 10
+    default: 10
+    locale_default:
+      zh_CN: 3
+      zh_TW: 3
   max_post_length:
     client: true
     default: 32000
@@ -454,17 +455,32 @@ posting:
   topic_featured_link_enabled:
     client: true
     default: true
-  body_min_entropy: 7
+  body_min_entropy:
+    default: 7
+    locale_default:
+      zh_CN: 3
+      zh_TW: 3
   min_topic_title_length:
     client: true
     default: 15
+    locale_default:
+      zh_CN: 6
+      zh_TW: 6
   max_topic_title_length:
     client: true
     default: 255
     max: 255
-  title_min_entropy: 10
+  title_min_entropy:
+    default: 10
+    locale_default:
+      zh_CN: 3
+      zh_TW: 3
   allow_uppercase_posts: false
-  title_prettify: true
+  title_prettify:
+    default: true
+    locale_default:
+      zh_CN: false
+      zh_TW: false
   title_fancy_entities: true
   min_private_message_title_length:
     client: true
@@ -478,9 +494,15 @@ posting:
   min_title_similar_length:
     client: true
     default: 10
+    locale_default:
+      zh_CN: 4
+      zh_TW: 4
   min_body_similar_length:
     client: true
     default: 15
+    locale_default:
+      zh_CN: 5
+      zh_TW: 5
   enable_private_messages:
     default: true
     client: true
@@ -524,7 +546,11 @@ posting:
   newuser_max_attachments:
     client: true
     default: 0
-  post_excerpt_maxlength: 300
+  post_excerpt_maxlength:
+    default: 300
+    locale_default:
+      zh_CN: 120
+      zh_TW: 120
   show_pinned_excerpt_mobile:
     client: true
     default: true
@@ -603,7 +629,11 @@ email:
     client: true
   private_email_time_window_seconds: 20
   email_posts_context: 5
-  digest_min_excerpt_length: 100
+  digest_min_excerpt_length:
+    default: 100
+    locale_default:
+      zh_CN: 50
+      zh_TW: 50
   digest_topics:
     default: 5
     min: 1
@@ -726,9 +756,7 @@ files:
     refresh: true
     type: list
   crawl_images:
-    default:
-      test: false
-      default: true
+    default: true
   max_image_width:
     client: true
     default: 690
@@ -736,9 +764,7 @@ files:
     client: true
     default: 500
   download_remote_images_to_local:
-    default:
-      test: false
-      default: true
+    default: true
   download_remote_images_threshold: 10
   download_remote_images_max_days_old:
     default: 30
@@ -908,7 +934,11 @@ security:
 
 onebox:
   enable_flash_video_onebox: false
-  post_onebox_maxlength: 500
+  post_onebox_maxlength:
+    default: 500
+    locale_default:
+      zh_CN: 200
+      zh_TW: 200
   onebox_domains_blacklist:
     default: ''
     type: list
@@ -954,10 +984,7 @@ spam:
   auto_block_first_post_regex: ""
 
 rate_limits:
-  unique_posts_mins:
-    default:
-      test: 0
-      default: 5
+  unique_posts_mins: 5
   rate_limit_create_topic: 15
   rate_limit_create_post: 5
   rate_limit_new_user_create_topic: 120
@@ -995,28 +1022,20 @@ rate_limits:
 
 developer:
   force_hostname:
-    hidden:
-      development: false
-      default: true
+    hidden: true
     default: ''
   port:
-    hidden:
-      development: false
-      default: true
-    default:
-      development: 3000
-      default: ''
+    hidden: true
+    default: ''
   queue_jobs:
-    hidden:
-      development: false
-      default: true
-    default:
-      test: false
-      default: true
+    hidden: true
+    default: true
   enable_long_polling:
     client: true
     default: true
-  long_polling_interval: 25000
+  long_polling_interval:
+    default: 25000
+    max: 25000
   long_polling_base_url:
     client: true
     default: '/'
@@ -1144,12 +1163,19 @@ search:
   min_search_term_length:
     client: true
     default: 3
+    locale_default:
+      zh_CN: 2
+      zh_TW: 2
 
   search_tokenize_chinese_japanese_korean: false
   search_prefer_recent_posts: false
-  search_recent_posts_size: 100000
+  search_recent_posts_size:
+    default: 100000
+    max: 100000
   log_search_queries: true
-  search_query_log_max_size: 1000000
+  search_query_log_max_size:
+    default: 1000000
+    max: 1000000
 
 uncategorized:
   version_checks:
@@ -1166,6 +1192,9 @@ uncategorized:
   slug_generation_method:
     default: 'ascii'
     enum: 'SlugSetting'
+    locale_default:
+      zh_CN: 'none'
+      zh_TW: 'none'
 
   permalink_normalizations:
     default: ''
@@ -1306,6 +1335,9 @@ uncategorized:
   read_time_word_count:
     default: 500
     client: true
+    locale_default:
+      zh_CN: 350
+      zh_TW: 350
 
   topic_page_title_includes_category: true
 
@@ -1323,7 +1355,7 @@ user_preferences:
   default_email_mailing_list_mode: false
   default_email_mailing_list_mode_frequency:
     enum: 'MailingListModeSiteSetting'
-    default: 0
+    default: 1
   disable_mailing_list_mode:
     default: false
     client: true
diff --git a/db/migrate/20170725075535_correct_default_email_mailing_list_mode_frequency.rb b/db/migrate/20170725075535_correct_default_email_mailing_list_mode_frequency.rb
new file mode 100644
index 00000000000..d2e4cdd0688
--- /dev/null
+++ b/db/migrate/20170725075535_correct_default_email_mailing_list_mode_frequency.rb
@@ -0,0 +1,8 @@
+class CorrectDefaultEmailMailingListModeFrequency < ActiveRecord::Migration
+  def up
+    execute "UPDATE site_settings SET value = '1' WHERE value = '0' AND name = 'default_email_mailing_list_mode_frequency';"
+  end
+
+  def down
+  end
+end
diff --git a/lib/discourse.rb b/lib/discourse.rb
index dd9d9d3fef9..cd6a27e4401 100644
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@@ -84,6 +84,8 @@ module Discourse
   # Cross site request forgery
   class CSRF < StandardError; end
 
+  class Deprecation < StandardError; end
+
   def self.filters
     @filters ||= [:latest, :unread, :new, :read, :posted, :bookmarks]
   end
diff --git a/lib/site_setting_extension.rb b/lib/site_setting_extension.rb
index 5b9fb8987d6..410f22bc17c 100644
--- a/lib/site_setting_extension.rb
+++ b/lib/site_setting_extension.rb
@@ -1,14 +1,16 @@
-require_dependency 'enum'
+require_dependency 'site_settings/deprecated_settings'
+require_dependency 'site_settings/type_supervisor'
+require_dependency 'site_settings/defaults_provider'
 require_dependency 'site_settings/db_provider'
-require 'site_setting_validations'
 
 module SiteSettingExtension
-  include SiteSettingValidations
+  include SiteSettings::DeprecatedSettings
+  extend Forwardable
 
-  # For plugins, so they can tell if a feature is supported
-  def supported_types
-    [:email, :username, :list, :enum]
-  end
+  def_delegator :defaults, :site_locale, :default_locale
+  def_delegator :defaults, :site_locale=, :default_locale=
+  def_delegator :defaults, :has_setting?
+  def_delegators 'SiteSettings::TypeSupervisor', :types, :supported_types
 
   # part 1 of refactor, centralizing the dependency here
   def provider=(val)
@@ -20,22 +22,6 @@ module SiteSettingExtension
     @provider ||= SiteSettings::DbProvider.new(SiteSetting)
   end
 
-  def types
-    @types ||= Enum.new(string: 1,
-                        time: 2,
-                        integer: 3,
-                        float: 4,
-                        bool: 5,
-                        null: 6,
-                        enum: 7,
-                        list: 8,
-                        url_list: 9,
-                        host_list: 10,
-                        category_list: 11,
-                        value_list: 12,
-                        regex: 13)
-  end
-
   def mutex
     @mutex ||= Mutex.new
   end
@@ -46,25 +32,17 @@ module SiteSettingExtension
   end
 
   def defaults
-    @defaults ||= {}
+    @defaults ||= SiteSettings::DefaultsProvider.new(self)
+  end
+
+  def type_supervisor
+    @type_supervisor ||= SiteSettings::TypeSupervisor.new(defaults)
   end
 
   def categories
     @categories ||= {}
   end
 
-  def enums
-    @enums ||= {}
-  end
-
-  def static_types
-    @static_types ||= {}
-  end
-
-  def choices
-    @choices ||= {}
-  end
-
   def shadowed_settings
     @shadowed_settings ||= []
   end
@@ -85,34 +63,14 @@ module SiteSettingExtension
     @previews ||= {}
   end
 
-  def validators
-    @validators ||= {}
-  end
-
   def setting(name_arg, default = nil, opts = {})
     name = name_arg.to_sym
     mutex.synchronize do
-      self.defaults[name] = default
+      defaults.load_setting(name,
+                            default,
+                            opts.extract!(*SiteSettings::DefaultsProvider::CONSUMED_OPTS))
+
       categories[name] = opts[:category] || :uncategorized
-      current_value = current.has_key?(name) ? current[name] : default
-
-      if enum = opts[:enum]
-        enums[name] = enum.is_a?(String) ? enum.constantize : enum
-        opts[:type] ||= :enum
-      end
-
-      if new_choices = opts[:choices]
-
-        new_choices = eval(new_choices) if new_choices.is_a?(String)
-
-        choices.has_key?(name) ?
-          choices[name].concat(new_choices) :
-          choices[name] = new_choices
-      end
-
-      if type = opts[:type]
-        static_types[name.to_sym] = type.to_sym
-      end
 
       if opts[:hidden]
         hidden_settings << name
@@ -124,7 +82,6 @@ module SiteSettingExtension
         unless val.nil? || (val == ''.freeze)
           hidden_settings << name
           shadowed_settings << name
-          current_value = val
         end
       end
 
@@ -132,31 +89,24 @@ module SiteSettingExtension
         refresh_settings << name
       end
 
+      if opts[:client]
+        client_settings << name.to_sym
+      end
+
       if opts[:preview]
         previews[name] = opts[:preview]
       end
 
-      opts[:validator] = opts[:validator].try(:constantize)
-      type = opts[:type] || get_data_type(name, defaults[name])
+      type_supervisor.load_setting(name,
+                                   opts.extract!(*SiteSettings::TypeSupervisor::CONSUMED_OPTS))
 
-      if validator_type = opts[:validator] || validator_for(type)
-        validators[name] = { class: validator_type, opts: opts }
-      end
-
-      current[name] = current_value
       setup_methods(name)
     end
   end
 
-  # just like a setting, except that it is available in javascript via DiscourseSession
-  def client_setting(name, default = nil, opts = {})
-    setting(name, default, opts)
-    client_settings << name.to_sym
-  end
-
   def settings_hash
     result = {}
-    @defaults.each do |s, _|
+    defaults.each_key do |s|
       result[s] = send(s).to_s
     end
     result
@@ -174,32 +124,21 @@ module SiteSettingExtension
 
   # Retrieve all settings
   def all_settings(include_hidden = false)
-    @defaults
-      .reject { |s, _| hidden_settings.include?(s) && !include_hidden }
+    defaults
+      .reject { |s, _| !include_hidden && hidden_settings.include?(s) }
       .map do |s, v|
-        value = send(s)
-        type = types[get_data_type(s, value)]
-        opts = {
-          setting: s,
-          description: description(s),
-          default: v.to_s,
-          type: type.to_s,
-          value: value.to_s,
-          category: categories[s],
-          preview: previews[s]
-        }
+      value = send(s)
+      opts = {
+        setting: s,
+        description: description(s),
+        default: defaults[s].to_s,
+        value: value.to_s,
+        category: categories[s],
+        preview: previews[s]
+      }.merge(type_supervisor.type_hash(s))
 
-        if type == :enum && enum_class(s)
-          opts.merge!(valid_values: enum_class(s).values, translate_names: enum_class(s).translate_names?)
-        elsif type == :enum
-          opts.merge!(valid_values: choices[s].map { |c| { name: c, value: c } }, translate_names: false)
-        end
-
-        opts[:textarea] = true if static_types[s] == :textarea
-
-        opts[:choices] = choices[s] if choices.has_key? s
-        opts
-      end
+      opts
+    end.unshift(defaults.locale_setting_hash)
   end
 
   def description(setting)
@@ -217,22 +156,22 @@ module SiteSettingExtension
   def refresh!
     mutex.synchronize do
       ensure_listen_for_changes
-      old = current
 
-      new_hash = Hash[*(provider.all.map { |s|
-        [s.name.intern, convert(s.value, s.data_type, s.name)]
+      new_hash = Hash[*(defaults.db_all.map { |s|
+        [s.name.to_sym, type_supervisor.to_rb_value(s.name, s.value, s.data_type)]
       }.to_a.flatten)]
 
-      # add defaults, cause they are cached
-      new_hash = defaults.merge(new_hash)
+      defaults_view = defaults.all
+
+      # add locale default and defaults based on default_locale, cause they are cached
+      new_hash = defaults_view.merge(new_hash)
 
       # add shadowed
       shadowed_settings.each { |ss| new_hash[ss] = GlobalSetting.send(ss) }
 
-      changes, deletions = diff_hash(new_hash, old)
-
+      changes, deletions = diff_hash(new_hash, current)
       changes.each   { |name, val| current[name] = val }
-      deletions.each { |name, val| current[name] = defaults[name] }
+      deletions.each { |name, _|   current[name] = defaults_view[name] }
 
       clear_cache!
     end
@@ -282,44 +221,9 @@ module SiteSettingExtension
   end
 
   def add_override!(name, val)
-    type = get_data_type(name, defaults[name.to_sym])
-
-    val = val.to_s if type == types[:string]
-
-    if type == types[:bool] && val != true && val != false
-      val = (val == "t" || val == "true") ? 't' : 'f'
-    end
-
-    if type == types[:integer] && !val.is_a?(Integer)
-      val = val.to_i
-    end
-
-    if type == types[:null] && val != ''
-      type = get_data_type(name, val)
-    end
-
-    if type == types[:enum]
-      val = val.to_i if defaults[name.to_sym].is_a?(Integer)
-      if enum_class(name)
-        raise Discourse::InvalidParameters.new(:value) unless enum_class(name).valid_value?(val)
-      else
-        raise Discourse::InvalidParameters.new(:value) unless choices[name].include?(val)
-      end
-    end
-
-    if v = validators[name]
-      validator = v[:class].new(v[:opts])
-      unless validator.valid_value?(val)
-        raise Discourse::InvalidParameters.new(validator.error_message)
-      end
-    end
-
-    if self.respond_to? "validate_#{name}"
-      send("validate_#{name}", val)
-    end
-
+    val, type = type_supervisor.to_db_value(name, val)
     provider.save(name, val, type)
-    current[name] = convert(val, type, name)
+    current[name] = type_supervisor.to_rb_value(name, val)
     notify_clients!(name) if client_settings.include? name
     clear_cache!
   end
@@ -332,26 +236,10 @@ module SiteSettingExtension
     MessageBus.publish('/client_settings', name: name, value: self.send(name))
   end
 
-  def has_setting?(name)
-    defaults.has_key?(name.to_sym) || defaults.has_key?("#{name}?".to_sym)
-  end
-
   def requires_refresh?(name)
     refresh_settings.include?(name.to_sym)
   end
 
-  def is_valid_data?(name, value)
-    valid = true
-    type = get_data_type(name, defaults[name.to_sym])
-
-    if type == types[:integer]
-      # validate integer
-      valid = false unless value.to_i.is_a?(Integer)
-    end
-
-    valid
-  end
-
   def filter_value(name, value)
     if %w[disabled_image_download_domains onebox_domains_blacklist exclude_rel_nofollow_domains email_domains_blacklist email_domains_whitelist white_listed_spam_host_domains].include? name
       domain_array = []
@@ -362,7 +250,7 @@ module SiteSettingExtension
   end
 
   def set(name, value)
-    if has_setting?(name) && is_valid_data?(name, value)
+    if has_setting?(name)
       value = filter_value(name, value)
       self.send("#{name}=", value)
       Discourse.request_refresh! if requires_refresh?(name)
@@ -399,90 +287,11 @@ module SiteSettingExtension
     [changes, deletions]
   end
 
-  def get_data_type(name, val)
-    return types[:null] if val.nil?
-
-    # Some types are just for validations like email.
-    # Only consider it valid if includes in `types`
-    if static_type = static_types[name.to_sym]
-      return types[static_type] if types.keys.include?(static_type)
-    end
-
-    case val
-    when String
-      types[:string]
-    when Integer
-      types[:integer]
-    when Float
-      types[:float]
-    when TrueClass, FalseClass
-      types[:bool]
-    else
-      raise ArgumentError.new :val
-    end
-  end
-
-  def convert(value, type, name)
-    case type
-    when types[:float]
-      value.to_f
-    when types[:integer]
-      value.to_i
-    when types[:bool]
-      value == true || value == "t" || value == "true"
-    when types[:null]
-      nil
-    when types[:enum]
-      defaults[name.to_sym].is_a?(Integer) ? value.to_i : value
-    else
-      return value if types[type]
-      # Otherwise it's a type error
-      raise ArgumentError.new :type
-    end
-  end
-
-  def validator_for(type_name)
-    @validator_mapping ||= {
-      'email'        => EmailSettingValidator,
-      'username'     => UsernameSettingValidator,
-      types[:integer] => IntegerSettingValidator,
-      types[:string] => StringSettingValidator,
-      'list' => StringSettingValidator,
-      'enum' => StringSettingValidator,
-      'regex' => RegexSettingValidator
-    }
-    @validator_mapping[type_name]
-  end
-
-  DEPRECATED_SETTINGS = [
-    ['use_https', 'force_https', '1.7']
-  ]
-
-  def setup_deprecated_methods
-    DEPRECATED_SETTINGS.each do |old_setting, new_setting, version|
-      define_singleton_method old_setting do
-        logger.warn("`SiteSetting.#{old_setting}` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}` instead")
-        self.public_send new_setting
-      end
-
-      define_singleton_method "#{old_setting}?" do
-        logger.warn("`SiteSetting.#{old_setting}?` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}?` instead")
-        self.public_send "#{new_setting}?"
-      end
-
-      define_singleton_method "#{old_setting}=" do |val|
-        logger.warn("`SiteSetting.#{old_setting}=` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}=` instead")
-        self.public_send "#{new_setting}=", val
-      end
-    end
-  end
-
   def setup_methods(name)
     clean_name = name.to_s.sub("?", "").to_sym
 
     define_singleton_method clean_name do
-      c = @containers[provider.current_site]
-      if c
+      if (c = @containers[provider.current_site])
         c[name]
       else
         refresh!
@@ -499,10 +308,6 @@ module SiteSettingExtension
     end
   end
 
-  def enum_class(name)
-    enums[name]
-  end
-
   def get_hostname(url)
     unless (URI.parse(url).scheme rescue nil).nil?
       url = "http://#{url}" if URI.parse(url).scheme.nil?
diff --git a/lib/site_settings/defaults_provider.rb b/lib/site_settings/defaults_provider.rb
new file mode 100644
index 00000000000..4b7b432912b
--- /dev/null
+++ b/lib/site_settings/defaults_provider.rb
@@ -0,0 +1,126 @@
+module SiteSettings; end
+
+# A cache for providing default value based on site locale
+class SiteSettings::DefaultsProvider
+  include Enumerable
+
+  CONSUMED_OPTS = %i[default locale_default].freeze
+  DEFAULT_LOCALE_KEY = :default_locale
+  DEFAULT_LOCALE = 'en'.freeze
+  DEFAULT_CATEGORY = 'required'.freeze
+
+  def initialize(site_setting)
+    @site_setting = site_setting
+    @site_setting.refresh_settings << DEFAULT_LOCALE_KEY
+
+    @cached = {}
+    @defaults = {}
+    @defaults[DEFAULT_LOCALE.to_sym] = {}
+    @site_locale = nil
+    refresh_site_locale!
+  end
+
+  def load_setting(name_arg, value, opts = {})
+    name = name_arg.to_sym
+    @defaults[DEFAULT_LOCALE.to_sym][name] = value
+
+    if (locale_default = opts[:locale_default])
+      locale_default.each do |locale, v|
+        locale = locale.to_sym
+        @defaults[locale] ||= {}
+        @defaults[locale][name] = v
+      end
+    end
+    refresh_cache!
+  end
+
+  def db_all
+    @site_setting.provider.all.delete_if { |s| s.name.to_sym == DEFAULT_LOCALE_KEY }
+  end
+
+  def all
+    @cached
+  end
+
+  def get(name)
+    @cached[name.to_sym]
+  end
+
+  # Used to override site settings in dev/test env
+  def set_regardless_of_locale(name, value)
+    name = name.to_sym
+    if @site_setting.has_setting?(name)
+      @defaults.each { |_, hash| hash.delete(name) }
+      @defaults[DEFAULT_LOCALE.to_sym][name] = value
+      value, type = @site_setting.type_supervisor.to_db_value(name, value)
+      @cached[name] = @site_setting.type_supervisor.to_rb_value(name, value, type)
+    else
+      raise ArgumentError.new("No setting named '#{name}' exists")
+    end
+  end
+
+  alias [] get
+
+  attr_reader :site_locale
+
+  def site_locale=(val)
+    val = val.to_s
+    raise Discourse::InvalidParameters.new(:value) unless LocaleSiteSetting.valid_value?(val)
+
+    if val != @site_locale
+      @site_setting.provider.save(DEFAULT_LOCALE_KEY, val, SiteSetting.types[:string])
+      refresh_site_locale!
+      @site_setting.refresh!
+      Discourse.request_refresh!
+    end
+
+    @site_locale
+  end
+
+  def each
+    @cached.each { |k, v| yield k.to_sym, v }
+  end
+
+  def locale_setting_hash
+    {
+      setting: DEFAULT_LOCALE_KEY,
+      default: DEFAULT_LOCALE,
+      category: DEFAULT_CATEGORY,
+      description: @site_setting.description(DEFAULT_LOCALE_KEY),
+      type: SiteSetting.types[SiteSetting.types[:enum]],
+      preview: nil,
+      value: @site_locale,
+      valid_values: LocaleSiteSetting.values,
+      translate_names: LocaleSiteSetting.translate_names?
+    }
+  end
+
+  def refresh_site_locale!
+    if GlobalSetting.respond_to?(DEFAULT_LOCALE_KEY) &&
+        (global_val = GlobalSetting.send(DEFAULT_LOCALE_KEY)) &&
+        !global_val.blank?
+      @site_locale = global_val
+    elsif (db_val = @site_setting.provider.find(DEFAULT_LOCALE_KEY))
+      @site_locale = db_val.value.to_s
+    else
+      @site_locale = DEFAULT_LOCALE
+    end
+    refresh_cache!
+    @site_locale
+  end
+
+  def has_setting?(name)
+    has_key?(name.to_sym) || has_key?("#{name.to_s}?".to_sym)
+  end
+
+  private
+
+  def has_key?(key)
+    @cached.key?(key) || key == DEFAULT_LOCALE_KEY
+  end
+
+  def refresh_cache!
+    @cached = @defaults[DEFAULT_LOCALE.to_sym].merge(@defaults.fetch(@site_locale.to_sym, {}))
+  end
+
+end
diff --git a/lib/site_settings/deprecated_settings.rb b/lib/site_settings/deprecated_settings.rb
new file mode 100644
index 00000000000..ca63777b4c3
--- /dev/null
+++ b/lib/site_settings/deprecated_settings.rb
@@ -0,0 +1,26 @@
+module SiteSettings; end
+
+module SiteSettings::DeprecatedSettings
+  DEPRECATED_SETTINGS = [
+    %w[use_https force_https 1.7]
+  ]
+
+  def setup_deprecated_methods
+    DEPRECATED_SETTINGS.each do |old_setting, new_setting, version|
+      define_singleton_method old_setting do
+        logger.warn("`SiteSetting.#{old_setting}` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}` instead")
+        self.public_send new_setting
+      end
+
+      define_singleton_method "#{old_setting}?" do
+        logger.warn("`SiteSetting.#{old_setting}?` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}?` instead")
+        self.public_send "#{new_setting}?"
+      end
+
+      define_singleton_method "#{old_setting}=" do |val|
+        logger.warn("`SiteSetting.#{old_setting}=` has been deprecated and will be removed in the #{version} Release. Please use `SiteSetting.#{new_setting}=` instead")
+        self.public_send "#{new_setting}=", val
+      end
+    end
+  end
+end
diff --git a/lib/site_settings/local_process_provider.rb b/lib/site_settings/local_process_provider.rb
index a9451505459..e3974b0ea4d 100644
--- a/lib/site_settings/local_process_provider.rb
+++ b/lib/site_settings/local_process_provider.rb
@@ -10,7 +10,7 @@ class SiteSettings::LocalProcessProvider
     @settings[current_site] ||= {}
   end
 
-  def initialize()
+  def initialize
     @settings = {}
     self.current_site = "test"
   end
diff --git a/lib/site_settings/type_supervisor.rb b/lib/site_settings/type_supervisor.rb
new file mode 100644
index 00000000000..0cd9f272bc9
--- /dev/null
+++ b/lib/site_settings/type_supervisor.rb
@@ -0,0 +1,210 @@
+require_dependency 'site_settings/validations'
+require_dependency 'enum'
+
+module SiteSettings; end
+
+class SiteSettings::TypeSupervisor
+  include SiteSettings::Validations
+
+  CONSUMED_OPTS = %i[enum choices type validator min max regex hidden regex_error].freeze
+  VALIDATOR_OPTS = %i[min max regex hidden regex_error].freeze
+
+  # For plugins, so they can tell if a feature is supported
+  SUPPORTED_TYPES = %i[email username list enum].freeze
+
+  def self.types
+    @types ||= Enum.new(string: 1,
+                        time: 2,
+                        integer: 3,
+                        float: 4,
+                        bool: 5,
+                        null: 6,
+                        enum: 7,
+                        list: 8,
+                        url_list: 9,
+                        host_list: 10,
+                        category_list: 11,
+                        value_list: 12,
+                        regex: 13,
+                        email: 14,
+                        username: 15)
+  end
+
+  def self.parse_value_type(val)
+    case val
+    when NilClass
+      self.types[:null]
+    when String
+      self.types[:string]
+    when Integer
+      self.types[:integer]
+    when Float
+      self.types[:float]
+    when TrueClass, FalseClass
+      self.types[:bool]
+    else
+      raise ArgumentError.new :val
+    end
+  end
+
+  def self.supported_types
+    SUPPORTED_TYPES
+  end
+
+  def initialize(defaults_provider)
+    @defaults_provider = defaults_provider
+    @enums = {}
+    @static_types = {}
+    @choices = {}
+    @validators = {}
+    @types = {}
+  end
+
+  def load_setting(name_arg, opts = {})
+    name = name_arg.to_sym
+
+    if (enum = opts[:enum])
+      @enums[name] = enum.is_a?(String) ? enum.constantize : enum
+      opts[:type] ||= :enum
+    end
+
+    if (new_choices = opts[:choices])
+      new_choices = eval(new_choices) if new_choices.is_a?(String)
+
+      if @choices.has_key?(name)
+        @choices[name].concat(new_choices)
+      else
+        @choices[name] = new_choices
+      end
+    end
+
+    if (type = opts[:type])
+      @static_types[name] = type.to_sym
+    end
+    @types[name] = get_data_type(name, @defaults_provider[name])
+
+    opts[:validator] = opts[:validator].try(:constantize)
+    if (validator_type = (opts[:validator] || validator_for(@types[name])))
+      @validators[name] = { class: validator_type, opts: opts.slice(*VALIDATOR_OPTS) }
+    end
+  end
+
+  def to_rb_value(name, value, override_type = nil)
+    name = name.to_sym
+    type = @types[name] = (override_type || @types[name] || get_data_type(name, value))
+
+    case type
+    when self.class.types[:float]
+      value.to_f
+    when self.class.types[:integer]
+      value.to_i
+    when self.class.types[:bool]
+      value == true || value == 't' || value == 'true'
+    when self.class.types[:null]
+      nil
+    when self.class.types[:enum]
+      @defaults_provider[name].is_a?(Integer) ? value.to_i : value.to_s
+    when self.class.types[:string]
+      value.to_s
+    else
+      return value if self.class.types[type]
+      # Otherwise it's a type error
+      raise ArgumentError.new :type
+    end
+  end
+
+  def to_db_value(name, value)
+    val, type = normalize_input(name, value)
+    validate_value(name, type, val)
+    [val, type]
+  end
+
+  def type_hash(name)
+    name = name.to_sym
+    type = self.class.types[@types[name]]
+
+    result = { type: type.to_s }
+
+    if type == :enum
+      if (klass = enum_class(name))
+        result.merge!(valid_values: klass.values, translate_names: klass.translate_names?)
+      else
+        result.merge!(valid_values: @choices[name].map { |c| { name: c, value: c } }, translate_names: false)
+      end
+    end
+
+    result[:choices] = @choices[name] if @choices.has_key? name
+    result
+  end
+
+  private
+
+  def normalize_input(name, val)
+    name = name.to_sym
+    type = @types[name] || self.class.parse_value_type(val)
+
+    if type == self.class.types[:bool]
+      val = (val == true || val == 't' || val == 'true') ? 't' : 'f'
+    elsif type == self.class.types[:integer] && !val.is_a?(Integer)
+      val = val.to_i
+    elsif type == self.class.types[:null] && val != ''
+      type = get_data_type(name, val)
+    elsif type == self.class.types[:enum]
+      val = @defaults_provider[name].is_a?(Integer) ? val.to_i : val.to_s
+    end
+
+    [val, type]
+  end
+
+  def validate_value(name, type, val)
+    if type == self.class.types[:enum]
+      if enum_class(name)
+        raise Discourse::InvalidParameters.new(:value) unless enum_class(name).valid_value?(val)
+      else
+        raise Discourse::InvalidParameters.new(:value) unless @choices[name].include?(val)
+      end
+    end
+
+    if (v = @validators[name])
+      validator = v[:class].new(v[:opts])
+      unless validator.valid_value?(val)
+        raise Discourse::InvalidParameters, "#{name.to_s}: #{validator.error_message}"
+      end
+    end
+
+    validate_method = "validate_#{name}"
+    if self.respond_to? validate_method
+      send(validate_method, val)
+    end
+  end
+
+  def get_data_type(name, val)
+    # Some types are just for validations like email.
+    # Only consider it valid if includes in `types`
+    if (static_type = @static_types[name.to_sym])
+      return self.class.types[static_type] if self.class.types.keys.include?(static_type)
+    end
+
+    self.class.parse_value_type(val)
+  end
+
+  def enum_class(name)
+    @enums[name]
+  end
+
+  def validator_for(type_name)
+    case type_name
+    when self.class.types[:email]
+      EmailSettingValidator
+    when self.class.types[:username]
+      UsernameSettingValidator
+    when self.class.types[:integer]
+      IntegerSettingValidator
+    when self.class.types[:regex]
+      RegexSettingValidator
+    when self.class.types[:string], self.class.types[:list], self.class.types[:enum]
+      StringSettingValidator
+    else nil
+    end
+  end
+end
diff --git a/lib/site_setting_validations.rb b/lib/site_settings/validations.rb
similarity index 97%
rename from lib/site_setting_validations.rb
rename to lib/site_settings/validations.rb
index 7858c68f0e8..0643ab49b6a 100644
--- a/lib/site_setting_validations.rb
+++ b/lib/site_settings/validations.rb
@@ -1,6 +1,6 @@
+module SiteSettings; end
 
-module SiteSettingValidations
-
+module SiteSettings::Validations
   def validate_error(key)
     raise Discourse::InvalidParameters.new(I18n.t("errors.site_settings.#{key}"))
   end
diff --git a/lib/site_settings/yaml_loader.rb b/lib/site_settings/yaml_loader.rb
index 5142f5aab1a..787be9848e2 100644
--- a/lib/site_settings/yaml_loader.rb
+++ b/lib/site_settings/yaml_loader.rb
@@ -1,32 +1,26 @@
 module SiteSettings; end
 
 class SiteSettings::YamlLoader
-
   def initialize(file)
     @file = file
   end
 
-  def env_val(value)
-    if value.is_a?(Hash)
-      value.has_key?(Rails.env) ? value[Rails.env] : value['default']
-    else
-      value
-    end
-  end
-
   def load
     yaml = YAML.load_file(@file)
     yaml.each_key do |category|
       yaml[category].each do |setting_name, hash|
         if hash.is_a?(Hash)
           # Get default value for the site setting:
-          value = env_val(hash.delete('default'))
-
-          if hash.key?('hidden')
-            hash['hidden'] = env_val(hash.delete('hidden'))
+          value = hash.delete('default')
+          if value.is_a?(Hash)
+            raise Discourse::Deprecation, "Site setting per env is no longer supported. Error setting: #{setting_name}"
           end
 
-          yield category, setting_name, value, hash.symbolize_keys!
+          if hash['hidden']&.is_a?(Hash)
+            raise Discourse::Deprecation, "Hidden site setting per env is no longer supported. Error setting: #{setting_name}"
+          end
+
+          yield category, setting_name, value, hash.deep_symbolize_keys!
         else
           # Simplest case. site_setting_name: 'default value'
           yield category, setting_name, hash, {}
diff --git a/plugins/discourse-narrative-bot/config/settings.yml b/plugins/discourse-narrative-bot/config/settings.yml
index e36e06f8a4d..c33d382ced0 100644
--- a/plugins/discourse-narrative-bot/config/settings.yml
+++ b/plugins/discourse-narrative-bot/config/settings.yml
@@ -1,8 +1,6 @@
 plugins:
   discourse_narrative_bot_enabled:
-    default:
-      default: true
-      test: false
+    default: true
     client: true
   disable_discourse_narrative_bot_welcome_post:
     default: false
diff --git a/script/benchmarks/site_setting/bench.rb b/script/benchmarks/site_setting/bench.rb
new file mode 100644
index 00000000000..1ac30060130
--- /dev/null
+++ b/script/benchmarks/site_setting/bench.rb
@@ -0,0 +1,48 @@
+require 'benchmark/ips'
+require File.expand_path('../../../../config/environment', __FILE__)
+
+# Put pre conditions here
+# Used db but it's OK in the most cases
+
+# build the cache
+SiteSetting.title = SecureRandom.hex
+SiteSetting.default_locale = SiteSetting.default_locale == 'en' ? 'zh_CN' : 'en'
+SiteSetting.refresh!
+
+tests = [
+  ["current cache", lambda do
+    SiteSetting.title
+    SiteSetting.enable_sso
+  end
+  ],
+  ["change default locale with current cache refreshed", lambda do
+    SiteSetting.default_locale = SiteSetting.default_locale == 'en' ? 'zh_CN' : 'en'
+  end
+  ],
+  ["change site setting", lambda do
+    SiteSetting.title = SecureRandom.hex
+  end
+  ],
+]
+
+Benchmark.ips do |x|
+  tests.each do |test, proc|
+    x.report(test, proc)
+  end
+end
+
+# 2017-08-02 - Erick's Site Setting change
+
+# Before
+# Calculating -------------------------------------
+# current cache    167.518k (±12.1%) i/s -    822.983k in   5.000478s
+# change default locale with current cache refreshed
+# 174.173  (±16.7%) i/s -    845.000  in   5.015281s
+# change site setting    132.956  (±16.5%) i/s -    663.000  in   5.124766s
+
+# After
+# Calculating -------------------------------------
+# current cache    167.170k (±12.2%) i/s -    824.688k in   5.022784s
+# change default locale with current cache refreshed
+# 79.876  (±16.3%) i/s -    392.000  in   5.067448s
+# change site setting    129.085  (±13.2%) i/s -    636.000  in   5.032536s
diff --git a/script/benchmarks/site_setting/profile.rb b/script/benchmarks/site_setting/profile.rb
new file mode 100644
index 00000000000..7b7237055d9
--- /dev/null
+++ b/script/benchmarks/site_setting/profile.rb
@@ -0,0 +1,32 @@
+require 'ruby-prof'
+
+def profile(&blk)
+  result = RubyProf.profile(&blk)
+  printer = RubyProf::GraphHtmlPrinter.new(result)
+  printer.print(STDOUT)
+end
+profile { '' } # loading profiler dependency
+
+require File.expand_path('../../../../config/environment', __FILE__)
+
+# warming up
+SiteSetting.title
+SiteSetting.enable_sso
+SiteSetting.default_locale = SiteSetting.default_locale == 'en' ? 'zh_CN' : 'en'
+SiteSetting.title = SecureRandom.hex
+
+profile do
+  SiteSetting.title
+end
+
+profile do
+  SiteSetting.enable_sso
+end
+
+profile do
+  SiteSetting.default_locale = SiteSetting.default_locale == 'en' ? 'zh_CN' : 'en'
+end
+
+profile do
+  SiteSetting.title = SecureRandom.hex
+end
diff --git a/spec/components/site_setting_extension_spec.rb b/spec/components/site_setting_extension_spec.rb
index 851ceec026e..5d87e8f9838 100644
--- a/spec/components/site_setting_extension_spec.rb
+++ b/spec/components/site_setting_extension_spec.rb
@@ -64,7 +64,7 @@ describe SiteSettingExtension do
       expect(settings.hello).to eq(99)
     end
 
-    it "Publishes changes cross sites" do
+    it "publishes changes cross sites" do
       settings.setting(:hello, 1)
       settings2.setting(:hello, 1)
 
@@ -143,7 +143,7 @@ describe SiteSettingExtension do
 
       it "should publish changes to clients" do
         settings.setting("test_setting", 100)
-        settings.client_setting("test_setting")
+        settings.setting("test_setting", nil, client: true)
 
         messages = MessageBus.track_publish do
           settings.test_setting = 88
@@ -155,8 +155,11 @@ describe SiteSettingExtension do
   end
 
   describe "remove_override" do
-    it "correctly nukes overrides" do
+    before do
       settings.setting(:test_override, "test")
+      settings.refresh!
+    end
+    it "correctly nukes overrides" do
       settings.test_override = "bla"
       settings.remove_override!(:test_override)
       expect(settings.test_override).to eq("test")
@@ -263,6 +266,7 @@ describe SiteSettingExtension do
       settings.setting(:test_int_enum, 1, enum: TestIntEnumClass)
       settings.test_int_enum = "2"
       settings.refresh!
+      expect(settings.defaults[:test_int_enum]).to eq(1)
       expect(settings.test_int_enum).to eq(2)
     end
 
@@ -272,7 +276,7 @@ describe SiteSettingExtension do
 
     class TestEnumClass
       def self.valid_value?(v)
-        true
+        self.values.include?(v)
       end
       def self.values
         ['en']
@@ -299,6 +303,10 @@ describe SiteSettingExtension do
       expect(settings.all_settings.detect { |s| s[:setting] == :test_enum }).to be_present
     end
 
+    it 'should report error when being set other values' do
+      expect { settings.test_enum = 'not_in_enum' }.to raise_error(Discourse::InvalidParameters)
+    end
+
     context 'when overridden' do
       after :each do
         settings.remove_override!(:validated_setting)
@@ -384,6 +392,14 @@ describe SiteSettingExtension do
     end
   end
 
+  describe ".set_and_log" do
+    it "raises an error when set for an invalid setting name" do
+      expect {
+        settings.set_and_log("provider", "haxxed")
+      }.to raise_error(ArgumentError)
+    end
+  end
+
   describe "filter domain name" do
     before do
       settings.setting(:white_listed_spam_host_domains, "www.example.com")
@@ -503,4 +519,62 @@ describe SiteSettingExtension do
     end
   end
 
+  describe 'locale default overrides are respected' do
+    before do
+      settings.setting(:test_override, 'default', locale_default: { zh_CN: 'cn' })
+      settings.refresh!
+    end
+
+    after do
+      settings.remove_override!(:test_override)
+    end
+
+    it 'ensures the default cache expired after overriding the default_locale' do
+      expect(settings.test_override).to eq('default')
+      settings.default_locale = 'zh_CN'
+      expect(settings.test_override).to eq('cn')
+    end
+
+    it 'returns the saved setting even locale default exists' do
+      expect(settings.test_override).to eq('default')
+      settings.default_locale = 'zh_CN'
+      settings.test_override = 'saved'
+      expect(settings.test_override).to eq('saved')
+    end
+  end
+
+  describe '.requires_refresh?' do
+    it 'always refresh default_locale always require refresh' do
+      expect(settings.requires_refresh?(:default_locale)).to be_truthy
+    end
+  end
+
+  describe '.default_locale' do
+    it 'is always loaded' do
+      expect(settings.default_locale).to eq 'en'
+    end
+  end
+
+  describe '.default_locale=' do
+    it 'can be changed' do
+      settings.default_locale = 'zh_CN'
+      expect(settings.default_locale).to eq 'zh_CN'
+    end
+
+    it 'refresh!' do
+      settings.expects(:refresh!)
+      settings.default_locale = 'zh_CN'
+    end
+
+    it 'expires the cache' do
+      settings.default_locale = 'zh_CN'
+      expect(Rails.cache.exist?(SiteSettingExtension.client_settings_cache_key)).to be_falsey
+    end
+
+    it 'refreshes the client' do
+      Discourse.expects(:request_refresh!)
+      settings.default_locale = 'zh_CN'
+    end
+  end
+
 end
diff --git a/spec/components/site_settings/defaults_provider_spec.rb b/spec/components/site_settings/defaults_provider_spec.rb
new file mode 100644
index 00000000000..01239fbff9b
--- /dev/null
+++ b/spec/components/site_settings/defaults_provider_spec.rb
@@ -0,0 +1,268 @@
+require 'rails_helper'
+require_dependency 'site_settings/defaults_provider'
+
+describe SiteSettings::DefaultsProvider do
+
+  let :provider_local do
+    SiteSettings::LocalProcessProvider.new
+  end
+
+  def new_settings(provider)
+    Class.new do
+      extend SiteSettingExtension
+      self.provider = provider
+    end
+  end
+
+  let :settings do
+    new_settings(provider_local)
+  end
+
+  describe 'inserts default_locale into refresh' do
+    it 'when initialize' do
+      expect(settings.refresh_settings.include?(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)).to be_truthy
+    end
+  end
+
+  describe '.db_all' do
+    it 'collects values from db except default locale' do
+      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
+                             'en',
+                             SiteSetting.types[:string])
+      expect(settings.defaults.db_all).to eq([])
+    end
+
+    it 'can collect values from db' do
+      settings.provider.save('try_a', 1, SiteSetting.types[:integer])
+      settings.provider.save('try_b', 2, SiteSetting.types[:integer])
+      expect(settings.defaults.db_all.count).to eq 2
+    end
+  end
+
+  describe 'expose default cache according to locale' do
+    before(:each) do
+      settings.setting(:test_override, 'default', locale_default: { zh_CN: 'cn' })
+      settings.setting(:test_default, 'test', regex: '^\S+$')
+      settings.refresh!
+    end
+
+    describe '.all' do
+      it 'returns all values according to the current locale' do
+        expect(settings.defaults.all).to eq(test_override: 'default', test_default: 'test')
+        settings.defaults.site_locale = 'zh_CN'
+        settings.defaults.refresh_site_locale!
+        expect(settings.defaults.all).to eq(test_override: 'cn', test_default: 'test')
+      end
+    end
+
+    describe '.get' do
+      it 'returns the default value to a site setting' do
+        expect(settings.defaults.get(:test_override)).to eq 'default'
+      end
+
+      it 'accepts a string as the parameters' do
+        expect(settings.defaults.get('test_override')).to eq 'default'
+      end
+
+      it 'returns the default value according to current locale' do
+        expect(settings.defaults.get(:test_override)).to eq 'default'
+        settings.defaults.site_locale = 'zh_CN'
+        expect(settings.defaults.get(:test_override)).to eq 'cn'
+      end
+    end
+
+    describe '.set_regardless_of_locale' do
+      let(:val) { 'env_overriden' }
+
+      it 'sets the default value to a site setting regardless the locale' do
+        settings.defaults.set_regardless_of_locale(:test_override, val)
+        expect(settings.defaults.get(:test_override)).to eq val
+        settings.defaults.site_locale = 'zh_CN'
+        expect(settings.defaults.get(:test_override)).to eq val
+      end
+
+      it 'handles the string' do
+        settings.defaults.set_regardless_of_locale('test_override', val)
+        expect(settings.defaults.get(:test_override)).to eq val
+      end
+
+      it 'converts the data type' do
+        settings.defaults.set_regardless_of_locale(:test_override, 1)
+        expect(settings.defaults.get(:test_override)).to eq '1'
+      end
+
+      it 'raises when the setting does not exists' do
+        expect {
+          settings.defaults.set_regardless_of_locale(:not_exist, 1)
+        }.to raise_error(ArgumentError)
+      end
+
+      it 'raises when the value is not valid' do
+        expect {
+          settings.defaults.set_regardless_of_locale(:test_default, 'regex will fail')
+        }.to raise_error(Discourse::InvalidParameters)
+      end
+    end
+
+    describe '.each' do
+      it 'yields the pair of site settings' do
+        expect { |b| settings.defaults.each(&b) }.to yield_successive_args([:test_override, 'default'], [:test_default, 'test'])
+        settings.defaults.site_locale = 'zh_CN'
+        expect { |b| settings.defaults.each(&b) }.to yield_successive_args([:test_override, 'cn'], [:test_default, 'test'])
+      end
+    end
+  end
+
+  describe '.site_locale' do
+    it 'returns the current site locale' do
+      expect(settings.defaults.site_locale).to eq 'en'
+    end
+
+    context 'when locale is set in the db' do
+      let(:db_val) { 'zr' }
+      let(:global_val) { 'gr' }
+
+      before do
+        settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
+                               db_val,
+                               SiteSetting.types[:string])
+        settings.defaults.refresh_site_locale!
+      end
+
+      it 'should load from database' do
+        expect(settings.defaults.site_locale).to eq db_val
+      end
+
+      it 'prioritizes GlobalSetting than value from db' do
+        GlobalSetting.stubs(:default_locale).returns(global_val)
+        settings.defaults.refresh_site_locale!
+        expect(settings.defaults.site_locale).to eq global_val
+      end
+
+      it 'ignores blank GlobalSetting' do
+        GlobalSetting.stubs(:default_locale).returns('')
+        settings.defaults.refresh_site_locale!
+        expect(settings.defaults.site_locale).to eq db_val
+      end
+    end
+
+  end
+
+  describe '.site_locale=' do
+    it 'changes and store the current site locale' do
+      settings.defaults.site_locale = 'zh_CN'
+      expect(settings.defaults.site_locale).to eq 'zh_CN'
+    end
+
+    it 'changes and store the current site locale' do
+      expect { settings.defaults.site_locale = 'random' }.to raise_error(Discourse::InvalidParameters)
+      expect(settings.defaults.site_locale).to eq 'en'
+    end
+
+    it "don't change when it's shadowed" do
+      GlobalSetting.stubs(:default_locale).returns('shadowed')
+      settings.defaults.site_locale = 'zh_CN'
+      expect(settings.defaults.site_locale).to eq 'shadowed'
+    end
+
+    it 'refresh_site_locale! when called' do
+      settings.defaults.expects(:refresh_site_locale!)
+      settings.defaults.site_locale = 'zh_CN'
+    end
+
+    it 'refreshes the client when changed' do
+      Discourse.expects(:request_refresh!).once
+      settings.defaults.site_locale = 'zh_CN'
+    end
+
+    it "doesn't refresh the client when changed" do
+      Discourse.expects(:request_refresh!).never
+      settings.defaults.site_locale = 'en'
+    end
+  end
+
+  describe '.locale_setting_hash' do
+    it 'returns the hash for client display' do
+      result = settings.defaults.locale_setting_hash
+
+      expect(result[:setting]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)
+      expect(result[:default]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE)
+      expect(result[:type]).to eq(SiteSetting.types[SiteSetting.types[:enum]])
+      expect(result[:preview]).to be_nil
+      expect(result[:value]).to eq(SiteSettings::DefaultsProvider::DEFAULT_LOCALE)
+      expect(result[:category]).to eq(SiteSettings::DefaultsProvider::DEFAULT_CATEGORY)
+      expect(result[:valid_values]).to eq(LocaleSiteSetting.values)
+      expect(result[:translate_names]).to eq(LocaleSiteSetting.translate_names?)
+      expect(result[:description]).not_to be_nil
+    end
+  end
+
+  describe '.load_setting' do
+    it 'adds a setting to the cache' do
+      settings.defaults.load_setting('new_a', 1)
+      expect(settings.defaults[:new_a]).to eq 1
+    end
+
+    it 'takes care of locale default' do
+      settings.defaults.load_setting(:new_b, 1, locale_default: { zh_CN: 2, zh_TW: 2 })
+      expect(settings.defaults[:new_b]).to eq 1
+    end
+  end
+
+  describe '.refresh_site_locale!' do
+    it 'loads the change to locale' do
+      expect(settings.defaults.site_locale).to eq 'en'
+      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
+                             'zh_CN',
+                             SiteSetting.types[:string])
+      settings.defaults.refresh_site_locale!
+      expect(settings.defaults.site_locale).to eq 'zh_CN'
+    end
+
+    it 'loads from GlobalSettings' do
+      expect(settings.defaults.site_locale).to eq 'en'
+      GlobalSetting.stubs(:default_locale).returns('fr')
+      settings.defaults.refresh_site_locale!
+      expect(settings.defaults.site_locale).to eq 'fr'
+    end
+
+    it 'prioritized GlobalSettings than db' do
+      expect(settings.defaults.site_locale).to eq 'en'
+      settings.provider.save(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY,
+                             'zh_CN',
+                             SiteSetting.types[:string])
+      GlobalSetting.stubs(:default_locale).returns('fr')
+      settings.defaults.refresh_site_locale!
+      expect(settings.defaults.site_locale).to eq 'fr'
+    end
+  end
+
+  describe '.has_setting?' do
+    before do
+      settings.setting(:r, 1)
+      settings.setting(:question?, 1)
+    end
+
+    it "returns true when it's present in the cache" do
+      expect(settings.defaults.has_setting?(:r)).to be_truthy
+    end
+
+    it '"responds when the arg is string' do
+      expect(settings.defaults.has_setting?('r')).to be_truthy
+    end
+
+    it 'default_locale always exists' do
+      expect(settings.defaults.has_setting?(SiteSettings::DefaultsProvider::DEFAULT_LOCALE_KEY)).to be_truthy
+    end
+
+    it 'returns false when the key is not exist' do
+      expect(settings.defaults.has_setting?('no_key')).to be_falsey
+    end
+
+    it 'checks name with question mark' do
+      expect(settings.defaults.has_setting?(:question)).to be_truthy
+      expect(settings.defaults.has_setting?('question')).to be_truthy
+    end
+  end
+
+end
diff --git a/spec/components/site_settings/type_supervisor_spec.rb b/spec/components/site_settings/type_supervisor_spec.rb
new file mode 100644
index 00000000000..3e4fbae1cd9
--- /dev/null
+++ b/spec/components/site_settings/type_supervisor_spec.rb
@@ -0,0 +1,341 @@
+require 'rails_helper'
+require_dependency 'site_settings/type_supervisor'
+
+describe SiteSettings::TypeSupervisor do
+  let :provider_local do
+    SiteSettings::LocalProcessProvider.new
+  end
+
+  def new_settings(provider)
+    Class.new do
+      extend SiteSettingExtension
+      self.provider = provider
+    end
+  end
+
+  let :settings do
+    new_settings(provider_local)
+  end
+
+  subject { SiteSettings::TypeSupervisor }
+
+  describe 'constants' do
+    it 'validator opts are the subset of consumed opts' do
+      expect(Set.new(SiteSettings::TypeSupervisor::CONSUMED_OPTS).superset?(
+        Set.new(SiteSettings::TypeSupervisor::VALIDATOR_OPTS))).to be_truthy
+    end
+  end
+
+  describe '#types' do
+    context "verify enum sequence" do
+      it "'string' should be at 1st position" do
+        expect(SiteSettings::TypeSupervisor.types[:string]).to eq(1)
+      end
+      it "'time' should be at 2nd position" do
+        expect(SiteSettings::TypeSupervisor.types[:time]).to eq(2)
+      end
+      it "'integer' should be at 3rd position" do
+        expect(SiteSettings::TypeSupervisor.types[:integer]).to eq(3)
+      end
+      it "'float' should be at 4th position" do
+        expect(SiteSettings::TypeSupervisor.types[:float]).to eq(4)
+      end
+      it "'bool' should be at 5th position" do
+        expect(SiteSettings::TypeSupervisor.types[:bool]).to eq(5)
+      end
+      it "'null' should be at 6th position" do
+        expect(SiteSettings::TypeSupervisor.types[:null]).to eq(6)
+      end
+      it "'enum' should be at 7th position" do
+        expect(SiteSettings::TypeSupervisor.types[:enum]).to eq(7)
+      end
+      it "'list' should be at 8th position" do
+        expect(SiteSettings::TypeSupervisor.types[:list]).to eq(8)
+      end
+      it "'url_list' should be at 9th position" do
+        expect(SiteSettings::TypeSupervisor.types[:url_list]).to eq(9)
+      end
+      it "'host_list' should be at 10th position" do
+        expect(SiteSettings::TypeSupervisor.types[:host_list]).to eq(10)
+      end
+      it "'category_list' should be at 11th position" do
+        expect(SiteSettings::TypeSupervisor.types[:category_list]).to eq(11)
+      end
+      it "'value_list' should be at 12th position" do
+        expect(SiteSettings::TypeSupervisor.types[:value_list]).to eq(12)
+      end
+      it "'regex' should be at 13th position" do
+        expect(SiteSettings::TypeSupervisor.types[:regex]).to eq(13)
+      end
+      it "'email' should be at 14th position" do
+        expect(SiteSettings::TypeSupervisor.types[:email]).to eq(14)
+      end
+      it "'username' should be at 15th position" do
+        expect(SiteSettings::TypeSupervisor.types[:username]).to eq(15)
+      end
+    end
+  end
+
+  describe '#parse_value_type' do
+    it 'returns :null type when the value is nil' do
+      expect(subject.parse_value_type(nil)).to eq(SiteSetting.types[:null])
+    end
+
+    it 'returns :integer type when the value is int' do
+      expect(subject.parse_value_type(2)).to eq(SiteSetting.types[:integer])
+    end
+
+    it 'returns :integer type when the value is large int' do
+      expect(subject.parse_value_type(99999999999999999999999999999999999)).to eq(SiteSetting.types[:integer])
+    end
+
+    it 'returns :float type when the value is float' do
+      expect(subject.parse_value_type(1.23)).to eq(SiteSetting.types[:float])
+    end
+
+    it 'returns :bool type when the value is true' do
+      expect(subject.parse_value_type(true)).to eq(SiteSetting.types[:bool])
+    end
+
+    it 'returns :bool type when the value is false' do
+      expect(subject.parse_value_type(false)).to eq(SiteSetting.types[:bool])
+    end
+
+    it 'raises when the value is not listed' do
+      expect {
+        subject.parse_value_type(Object.new)
+      }.to raise_error ArgumentError
+    end
+
+  end
+
+  context 'with different data types' do
+    class TestEnumClass
+      def self.valid_value?(v)
+        self.values.include?(v)
+      end
+      def self.values
+        ['en']
+      end
+      def self.translate_names?
+        false
+      end
+    end
+
+    class TestSmallThanTenValidator
+      def initialize(opts)
+      end
+      def valid_value?(v)
+        v < 10
+      end
+      def error_message
+        ''
+      end
+    end
+
+    before do
+      settings.setting(:type_null, nil)
+      settings.setting(:type_int, 1)
+      settings.setting(:type_true, true)
+      settings.setting(:type_false, false)
+      settings.setting(:type_float, 2.3232)
+      settings.setting(:type_string, 'string')
+      settings.setting(:type_enum_default_string, '2', type: 'enum', choices: ['2'])
+      settings.setting(:type_enum_class, 'en', enum: 'TestEnumClass')
+      settings.setting(:type_validator, 5, validator: 'TestSmallThanTenValidator')
+      settings.setting(:type_mock_validate_method, 'no_value')
+      settings.setting(:type_custom, 'custom', type: 'list')
+      settings.refresh!
+    end
+
+    describe '.to_db_value' do
+      let(:true_val) { 't' }
+      let(:false_val) { 'f' }
+
+      it 'returns nil value' do
+        expect(settings.type_supervisor.to_db_value(:type_null, nil)).to eq [nil, SiteSetting.types[:null]]
+      end
+
+      it 'gives a second chance to guess even told :null type' do
+        expect(settings.type_supervisor.to_db_value(:type_null, 1)).to eq [1, SiteSetting.types[:integer]]
+      end
+
+      it 'writes `t` or `f` given the possible bool value' do
+        expect(settings.type_supervisor.to_db_value(:type_true, true)).to eq [true_val, SiteSetting.types[:bool]]
+        expect(settings.type_supervisor.to_db_value(:type_true, 't')).to eq [true_val, SiteSetting.types[:bool]]
+        expect(settings.type_supervisor.to_db_value(:type_true, 'true')).to eq [true_val, SiteSetting.types[:bool]]
+        expect(settings.type_supervisor.to_db_value(:type_true, false)).to eq [false_val, SiteSetting.types[:bool]]
+      end
+
+      it 'writes `f` if given not `true` value' do
+        expect(settings.type_supervisor.to_db_value(:type_true, '')).to eq [false_val, SiteSetting.types[:bool]]
+        expect(settings.type_supervisor.to_db_value(:type_true, nil)).to eq [false_val, SiteSetting.types[:bool]]
+      end
+
+      it 'returns floats value' do
+        expect(settings.type_supervisor.to_db_value(:type_float, 1.2)).to eq [1.2, SiteSetting.types[:float]]
+        expect(settings.type_supervisor.to_db_value(:type_float, 1)).to eq [1.0, SiteSetting.types[:float]]
+      end
+
+      it 'returns string value' do
+        expect(settings.type_supervisor.to_db_value(:type_string, 'a')).to eq ['a', SiteSetting.types[:string]]
+      end
+
+      it 'returns enum value with string default' do
+        expect(settings.type_supervisor.to_db_value(:type_enum_default_string, 2)).to eq ['2', SiteSetting.types[:enum]]
+        expect(settings.type_supervisor.to_db_value(:type_enum_default_string, '2')).to eq ['2', SiteSetting.types[:enum]]
+      end
+
+      it 'raises when it does not in the enum choices' do
+        expect {
+          settings.type_supervisor.to_db_value(:type_enum_default_string, 'random')
+        }.to raise_error Discourse::InvalidParameters
+      end
+
+      it 'returns enum value for the given enum class' do
+        expect(settings.type_supervisor.to_db_value(:type_enum_class, 'en')).to eq ['en', SiteSetting.types[:enum]]
+      end
+
+      it 'raises when it does not in the enum class' do
+        expect {
+          settings.type_supervisor.to_db_value(:type_enum_class, 'random')
+        }.to raise_error Discourse::InvalidParameters
+      end
+
+      it 'validates value by validator' do
+        expect(settings.type_supervisor.to_db_value(:type_validator, 1)).to eq [1, SiteSetting.types[:integer]]
+      end
+
+      it 'raises when the validator says so' do
+        expect {
+          settings.type_supervisor.to_db_value(:type_validator, 11)
+        }.to raise_error Discourse::InvalidParameters
+      end
+
+      it 'tries invoke validate methods' do
+        settings.type_supervisor.expects(:validate_type_mock_validate_method).with('no')
+        settings.type_supervisor.to_db_value(:type_mock_validate_method, 'no')
+      end
+    end
+
+    describe '.to_rb_value' do
+      let(:true_val) { 't' }
+      let(:false_val) { 'f' }
+
+      it 'the type can be overriden by a parameter' do
+        expect(settings.type_supervisor.to_rb_value(:type_null, '1', SiteSetting.types[:integer])).to eq(1)
+      end
+
+      it 'returns nil value' do
+        expect(settings.type_supervisor.to_rb_value(:type_null, '1')).to eq nil
+        expect(settings.type_supervisor.to_rb_value(:type_null, 1)).to eq nil
+        expect(settings.type_supervisor.to_rb_value(:type_null, 'null')).to eq nil
+        expect(settings.type_supervisor.to_rb_value(:type_null, 'nil')).to eq nil
+      end
+
+      it 'returns true when it is true or `t` or `true`' do
+        expect(settings.type_supervisor.to_rb_value(:type_true, true)).to eq true
+        expect(settings.type_supervisor.to_rb_value(:type_true, 't')).to eq true
+        expect(settings.type_supervisor.to_rb_value(:type_true, 'true')).to eq true
+      end
+
+      it 'returns false if not one of `true` value' do
+        expect(settings.type_supervisor.to_rb_value(:type_true, 'tr')).to eq false
+        expect(settings.type_supervisor.to_rb_value(:type_true, '')).to eq false
+        expect(settings.type_supervisor.to_rb_value(:type_true, nil)).to eq false
+        expect(settings.type_supervisor.to_rb_value(:type_true, false)).to eq false
+        expect(settings.type_supervisor.to_rb_value(:type_true, 'f')).to eq false
+        expect(settings.type_supervisor.to_rb_value(:type_true, 'false')).to eq false
+      end
+
+      it 'returns float value' do
+        expect(settings.type_supervisor.to_rb_value(:type_float, 1.2)).to eq 1.2
+        expect(settings.type_supervisor.to_rb_value(:type_float, 1)).to eq 1.0
+        expect(settings.type_supervisor.to_rb_value(:type_float, '2.2')).to eq 2.2
+        expect(settings.type_supervisor.to_rb_value(:type_float, '2')).to eq 2
+      end
+
+      it 'returns string value' do
+        expect(settings.type_supervisor.to_rb_value(:type_string, 'a')).to eq 'a'
+        expect(settings.type_supervisor.to_rb_value(:type_string, 2)).to eq '2'
+      end
+
+      it 'returns value with string default' do
+        expect(settings.type_supervisor.to_rb_value(:type_enum_default_string, 2)).to eq '2'
+        expect(settings.type_supervisor.to_rb_value(:type_enum_default_string, '2')).to eq '2'
+      end
+
+      it 'returns value with a custom type' do
+        expect(settings.type_supervisor.to_rb_value(:type_custom, 2)).to eq 2
+        expect(settings.type_supervisor.to_rb_value(:type_custom, '2|3')).to eq '2|3'
+      end
+    end
+  end
+
+  describe '.type_hash' do
+    class TestEnumClass2
+      def self.valid_value?(v)
+        self.values.include?(v)
+      end
+      def self.values
+        ['a', 'b']
+      end
+      def self.translate_names?
+        false
+      end
+    end
+
+    before do
+      settings.setting(:type_null, nil)
+      settings.setting(:type_int, 1)
+      settings.setting(:type_true, true)
+      settings.setting(:type_float, 2.3232)
+      settings.setting(:type_string, 'string')
+      settings.setting(:type_url_list, 'string', type: 'url_list')
+      settings.setting(:type_enum_choices, '2', type: 'enum', choices: ['1', '2'])
+      settings.setting(:type_enum_class, 'a', enum: 'TestEnumClass2')
+      settings.setting(:type_list, 'a', type: 'list', choices: ['a', 'b'])
+      settings.refresh!
+    end
+
+    it 'returns null type' do
+      expect(settings.type_supervisor.type_hash(:type_null)[:type]).to eq 'null'
+    end
+    it 'returns int type' do
+      expect(settings.type_supervisor.type_hash(:type_int)[:type]).to eq 'integer'
+    end
+    it 'returns bool type' do
+      expect(settings.type_supervisor.type_hash(:type_true)[:type]).to eq 'bool'
+    end
+    it 'returns float type' do
+      expect(settings.type_supervisor.type_hash(:type_float)[:type]).to eq 'float'
+    end
+    it 'returns string type' do
+      expect(settings.type_supervisor.type_hash(:type_string)[:type]).to eq 'string'
+    end
+    it 'returns url_list type' do
+      expect(settings.type_supervisor.type_hash(:type_url_list)[:type]).to eq 'url_list'
+    end
+    it 'returns enum type' do
+      expect(settings.type_supervisor.type_hash(:type_enum_choices)[:type]).to eq 'enum'
+    end
+
+    it 'returns list choices' do
+      expect(settings.type_supervisor.type_hash(:type_list)[:choices]).to eq ['a', 'b']
+    end
+
+    it 'returns enum choices' do
+      hash = settings.type_supervisor.type_hash(:type_enum_choices)
+      expect(hash[:valid_values]).to eq [{ name: '1', value: '1' }, { name: '2', value: '2' }]
+      expect(hash[:translate_names]).to eq false
+    end
+
+    it 'returns enum class' do
+      hash = settings.type_supervisor.type_hash(:type_enum_class)
+      expect(hash[:valid_values]).to eq ['a', 'b']
+      expect(hash[:translate_names]).to eq false
+    end
+
+  end
+
+end
diff --git a/spec/components/site_settings/yaml_loader_spec.rb b/spec/components/site_settings/yaml_loader_spec.rb
index 7354cb04fd4..52e1952999f 100644
--- a/spec/components/site_settings/yaml_loader_spec.rb
+++ b/spec/components/site_settings/yaml_loader_spec.rb
@@ -8,26 +8,18 @@ describe SiteSettings::YamlLoader do
 
     def load_yaml(file_arg)
       SiteSettings::YamlLoader.new(file_arg).load do |category, name, default, opts|
-        if opts.delete(:client)
-          client_setting(category, name, default, opts)
-        else
-          setting(category, name, default, opts)
-        end
+        setting(category, name, default, opts)
       end
     end
 
     def setting(category, name, default = nil, opts = {})
       @settings ||= []
+      @client_settings ||= []
       @settings << name
       @categories ||= []
       @categories << category
       @categories.uniq!
-    end
-
-    def client_setting(category, name, default = nil)
-      @client_settings ||= []
-      @client_settings << name
-      setting(category, name, default)
+      @client_settings << name if opts.has_key?(:client)
     end
   end
 
@@ -36,7 +28,9 @@ describe SiteSettings::YamlLoader do
   let(:client)      { "#{Rails.root}/spec/fixtures/site_settings/client.yml" }
   let(:enum)        { "#{Rails.root}/spec/fixtures/site_settings/enum.yml" }
   let(:enum_client) { "#{Rails.root}/spec/fixtures/site_settings/enum_client.yml" }
-  let(:env)         { "#{Rails.root}/spec/fixtures/site_settings/env.yml" }
+  let(:deprecated_env) { "#{Rails.root}/spec/fixtures/site_settings/deprecated_env.yml" }
+  let(:deprecated_hidden) { "#{Rails.root}/spec/fixtures/site_settings/deprecated_hidden.yml" }
+  let(:locale_default) { "#{Rails.root}/spec/fixtures/site_settings/locale_default.yml" }
 
   it "loads simple settings" do
     receiver.expects(:setting).with('category1', 'title', 'My Site', {}).once
@@ -57,9 +51,9 @@ describe SiteSettings::YamlLoader do
   end
 
   it "can load client settings" do
-    receiver.expects(:client_setting).with('category1', 'title', 'Discourse', {})
-    receiver.expects(:client_setting).with('category2', 'tos_url', '', {})
-    receiver.expects(:client_setting).with('category2', 'must_approve_users', false, {})
+    receiver.expects(:setting).with('category1', 'title', 'Discourse', client: true)
+    receiver.expects(:setting).with('category2', 'tos_url', '', client: true)
+    receiver.expects(:setting).with('category2', 'must_approve_users', false, client: true)
     receiver.load_yaml(client)
   end
 
@@ -69,15 +63,22 @@ describe SiteSettings::YamlLoader do
   end
 
   it "can load enum client settings" do
-    receiver.expects(:client_setting).with do |category, name, default, opts|
-      category == ('basics') && name == ('default_locale') && default == ('en') && opts[:enum] == ('LocaleSiteSetting')
+    receiver.expects(:setting).with do |category, name, default, opts|
+      category == ('basics') && name == ('default_locale') && default == ('en') && opts[:enum] == ('LocaleSiteSetting') && opts[:client] == true
     end
     receiver.load_yaml(enum_client)
   end
 
-  it "can load settings based on environment" do
-    receiver.expects(:setting).with('misc', 'port', '', {})
-    receiver.expects(:client_setting).with('misc', 'crawl_images', false, {})
-    receiver.load_yaml(env)
+  it "raises deprecation when load settings based on environment" do
+    expect { receiver.load_yaml(deprecated_env) }.to raise_error(Discourse::Deprecation)
+  end
+
+  it "raises deprecation when hidden property is based on environment" do
+    expect { receiver.load_yaml(deprecated_hidden) }.to raise_error(Discourse::Deprecation)
+  end
+
+  it "can load settings with locale default" do
+    receiver.expects(:setting).with('search', 'min_search_term_length', 3, min: 2, client: true, locale_default: { zh_CN: 2, zh_TW: 2 })
+    receiver.load_yaml(locale_default)
   end
 end
diff --git a/spec/controllers/admin/site_settings_controller_spec.rb b/spec/controllers/admin/site_settings_controller_spec.rb
index 7a2de2d6d0f..6193572987e 100644
--- a/spec/controllers/admin/site_settings_controller_spec.rb
+++ b/spec/controllers/admin/site_settings_controller_spec.rb
@@ -27,6 +27,7 @@ describe Admin::SiteSettingsController do
 
       before do
         SiteSetting.setting(:test_setting, "default")
+        SiteSetting.refresh!
       end
 
       it 'sets the value when the param is present' do
@@ -49,6 +50,7 @@ describe Admin::SiteSettingsController do
 
       it 'does not allow changing of hidden settings' do
         SiteSetting.setting(:hidden_setting, "hidden", hidden: true)
+        SiteSetting.refresh!
         result = xhr :put, :update, id: 'hidden_setting', hidden_setting: 'not allowed'
         expect(SiteSetting.hidden_setting).to eq("hidden")
         expect(result.status).to eq(422)
diff --git a/spec/fixtures/site_settings/env.yml b/spec/fixtures/site_settings/deprecated_env.yml
similarity index 100%
rename from spec/fixtures/site_settings/env.yml
rename to spec/fixtures/site_settings/deprecated_env.yml
diff --git a/spec/fixtures/site_settings/deprecated_hidden.yml b/spec/fixtures/site_settings/deprecated_hidden.yml
new file mode 100644
index 00000000000..ba483cbb0db
--- /dev/null
+++ b/spec/fixtures/site_settings/deprecated_hidden.yml
@@ -0,0 +1,6 @@
+developer:
+  force_hostname:
+    hidden:
+      development: false
+      default: true
+    default: ''
diff --git a/spec/fixtures/site_settings/locale_default.yml b/spec/fixtures/site_settings/locale_default.yml
new file mode 100644
index 00000000000..9da10c8f39d
--- /dev/null
+++ b/spec/fixtures/site_settings/locale_default.yml
@@ -0,0 +1,8 @@
+search:
+  min_search_term_length:
+    client: true
+    default: 3
+    locale_default:
+      zh_CN: 2
+      zh_TW: 2
+    min: 2
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 986bde936c9..0a983d995bd 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -80,8 +80,8 @@ Spork.prefork do
       #  and pretend they are default.
       # There are a bunch of settings that are seeded, they must be loaded as defaults
       SiteSetting.current.each do |k, v|
-        # skip setting defauls for settings that are in unloaded plugins
-        SiteSetting.defaults[k] = v if SiteSetting.respond_to? k
+        # skip setting defaults for settings that are in unloaded plugins
+        SiteSetting.defaults.set_regardless_of_locale(k, v) if SiteSetting.respond_to? k
       end
 
       require_dependency 'site_settings/local_process_provider'
@@ -119,6 +119,7 @@ Spork.prefork do
       SiteSetting.provider.all.each do |setting|
         SiteSetting.remove_override!(setting.name)
       end
+      SiteSetting.defaults.site_locale = SiteSettings::DefaultsProvider::DEFAULT_LOCALE
 
       # very expensive IO operations
       SiteSetting.automatically_download_gravatars = false