diff --git a/app/assets/javascripts/discourse.js b/app/assets/javascripts/discourse.js
index ab0a429832b..48e0b663d42 100644
--- a/app/assets/javascripts/discourse.js
+++ b/app/assets/javascripts/discourse.js
@@ -6,6 +6,8 @@ define('ember', ['exports'], function(__exports__) {
   __exports__.default = Ember;
 });
 
+var _pluginCallbacks = [];
+
 window.Discourse = Ember.Application.createWithMixins(Discourse.Ajax, {
   rootElement: '#main',
   _docTitle: document.title,
@@ -127,6 +129,18 @@ window.Discourse = Ember.Application.createWithMixins(Discourse.Ajax, {
       }
     });
 
+    // Plugins that are registered via `<script>` tags.
+    var withPluginApi = require('discourse/lib/plugin-api').withPluginApi;
+    var initCount = 0;
+    _pluginCallbacks.forEach(function(cb) {
+      Discourse.instanceInitializer({
+        name: "_discourse_plugin_" + (++initCount),
+        after: 'inject-objects',
+        initialize: function() {
+          withPluginApi(cb.version, cb.code);
+        }
+      });
+    });
   },
 
   requiresRefresh: function(){
@@ -134,6 +148,9 @@ window.Discourse = Ember.Application.createWithMixins(Discourse.Ajax, {
     return desired && Discourse.get("currentAssetVersion") !== desired;
   }.property("currentAssetVersion", "desiredAssetVersion"),
 
+  _registerPluginCode(version, code) {
+    _pluginCallbacks.push({ version: version, code: code });
+  },
 
   assetVersion: Ember.computed({
     get: function() {
diff --git a/app/models/site_customization.rb b/app/models/site_customization.rb
index bc83a126bdb..b90c7018720 100644
--- a/app/models/site_customization.rb
+++ b/app/models/site_customization.rb
@@ -27,6 +27,17 @@ class SiteCustomization < ActiveRecord::Base
     raise e
   end
 
+  def transpile(es6_source, version)
+    template  = Tilt::ES6ModuleTranspilerTemplate.new {}
+    wrapped = <<PLUGIN_API_JS
+Discourse._registerPluginCode('#{version}', api => {
+  #{es6_source}
+});
+PLUGIN_API_JS
+
+    template.babel_transpile(wrapped)
+  end
+
   def process_html(html)
     doc = Nokogiri::HTML.fragment(html)
     doc.css('script[type="text/x-handlebars"]').each do |node|
@@ -43,6 +54,17 @@ SCRIPT
       node.replace("<script>#{compiled}</script>")
     end
 
+    doc.css('script[type="text/discourse-plugin"]').each do |node|
+      if node['version'].present?
+        begin
+          code = transpile(node.inner_html, node['version'])
+          node.replace("<script>#{code}</script>")
+        rescue Tilt::ES6ModuleTranspilerTemplate::JavaScriptError => ex
+          node.replace("<script type='text/discourse-js-error'>#{ex.message}</script>")
+        end
+      end
+    end
+
     doc.to_s
   end
 
diff --git a/lib/es6_module_transpiler/tilt/es6_module_transpiler_template.rb b/lib/es6_module_transpiler/tilt/es6_module_transpiler_template.rb
index d54524fe68a..b0d6f1b9172 100644
--- a/lib/es6_module_transpiler/tilt/es6_module_transpiler_template.rb
+++ b/lib/es6_module_transpiler/tilt/es6_module_transpiler_template.rb
@@ -94,6 +94,14 @@ module Tilt
       @@whitelisted.include?(path) || path =~ /discourse\/mixins/
     end
 
+    def babel_transpile(source)
+      klass = self.class
+      klass.protect do
+        klass.v8['console'] = Console.new("BABEL: babel-eval: ")
+        @output = klass.v8.eval(babel_source(source))
+      end
+    end
+
     def evaluate(scope, locals, &block)
       return @output if @output
 
@@ -139,11 +147,15 @@ module Tilt
       @output
     end
 
+    def babel_source(source)
+      js_source = ::JSON.generate(source, quirks_mode: true)
+      "babel.transform(#{js_source}, {ast: false, whitelist: ['es6.constants', 'es6.properties.shorthand', 'es6.arrowFunctions', 'es6.blockScoping', 'es6.destructuring', 'es6.spread', 'es6.parameters', 'es6.templateLiterals', 'es6.regex.unicode', 'es7.decorators', 'es6.classes']})['code']"
+    end
+
     private
 
     def generate_source(scope)
-      js_source = ::JSON.generate(data, quirks_mode: true)
-      js_source = "babel.transform(#{js_source}, {ast: false, whitelist: ['es6.constants', 'es6.properties.shorthand', 'es6.arrowFunctions', 'es6.blockScoping', 'es6.destructuring', 'es6.spread', 'es6.parameters', 'es6.templateLiterals', 'es6.regex.unicode', 'es7.decorators', 'es6.classes']})['code']"
+      js_source = babel_source(data)
       "new module.exports.Compiler(#{js_source}, '#{module_name(scope.root_path, scope.logical_path)}', #{compiler_options}).#{compiler_method}()"
     end
 
diff --git a/spec/models/site_customization_spec.rb b/spec/models/site_customization_spec.rb
index 571e95ddd08..ca87b12bcac 100644
--- a/spec/models/site_customization_spec.rb
+++ b/spec/models/site_customization_spec.rb
@@ -119,4 +119,37 @@ HTML
     expect(SiteCustomization.custom_head_tag).to match(/<b>test<\/b>/)
   end
 
+  context "plugin api" do
+    def transpile(html)
+      c = SiteCustomization.create!(user_id: -1, name: "test", head_tag: html, body_tag: html)
+      c.head_tag_baked
+    end
+
+    it "transpiles ES6 code" do
+      html = <<HTML
+        <script type='text/discourse-plugin' version='0.1'>
+          const x = 1;
+        </script>
+HTML
+
+      transpiled = transpile(html)
+      expect(transpiled).to match(/\<script\>/)
+      expect(transpiled).to match(/var x = 1;/)
+      expect(transpiled).to match(/_registerPluginCode\('0.1'/)
+    end
+
+    it "converts errors to a script type that is not evaluated" do
+      html = <<HTML
+        <script type='text/discourse-plugin' version='0.1'>
+          const x = 1;
+          x = 2;
+        </script>
+HTML
+
+      transpiled = transpile(html)
+      expect(transpiled).to match(/text\/discourse-js-error/)
+      expect(transpiled).to match(/read-only/)
+    end
+  end
+
 end