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Ember CLI Rails

Unify your EmberCLI and Rails Workflows!

EmberCLI-Rails is designed to give you the best of both worlds:

  • Stay up to date with the latest JavaScript technology and EmberCLI addons
  • Develop your Rails API and Ember front-ends from within a single process
  • Inject Rails-generated content into your EmberCLI application
  • Avoid Cross-Origin Resource Sharing gotchas by serving your EmberCLI applications and your API from a single domain
  • Write truly end-to-end integration tests, exercising your application's entire stack through JavaScript-enabled Capybara tests
  • Deploy your entire suite of applications to Heroku with a single git push

If you're having trouble, checkout the example project!

EmberCLI-Rails Supports EmberCLI 1.13.13 and later.


Add the following to your Gemfile:

gem "ember-cli-rails"

Then run bundle install:

$ bundle install

If you haven't created an Ember application yet, generate a new one:

$ ember new frontend --skip-git


First, generate the gem's initializer:

$ rails generate ember:init

This will create the following initializer:

# config/initializers/ember.rb

EmberCli.configure do |c| :frontend

This initializer assumes that your Ember application exists in Rails.root.join("frontend").

If this is not the case, you could

  • move your existing Ember application into Rails.root.join("frontend")
  • configure frontend to reference the Ember application in its current directory: :frontend, path: "~/projects/my-ember-app"

Initializer options

  • name - this represents the name of the Ember CLI application.

  • path - the path where your Ember CLI application is located. The default value is the name of your app in the Rails root.

  • silent - this provides --silent option for Ember CLI commands to control verbosity of their output.

  • yarn - enables the yarn package manager when installing dependencies

EmberCli.configure do |c| :adminpanel # path defaults to `Rails.root.join("adminpanel")` :frontend,
    path: "/path/to/your/ember-cli-app/on/disk" :payments, silent: true # by default it's false

Next, install the ember-cli-rails-addon:

$ cd path/to/frontend
$ ember install ember-cli-rails-addon

Be sure that the addon's MAJOR and MINOR version matches the gem's MAJOR and MINOR versions.

For instance, if you're using the 0.6.x version of the gem, specify ~> 0.6.0 in your Ember app's package.json:

  "devDependencies": {
    "ember-cli-rails-addon": "~> 0.6.0"


Configure Rails to route requests to the frontend Ember application:

# config/routes.rb

Rails.application.routes.draw do
  mount_ember_app :frontend, to: "/"

Routing options

  • to - The path to handle as an Ember application. This will only apply to format: :html requests. Additionally, this will handle child routes as well. For instance, mounting mount_ember_app :frontend, to: "/frontend" will handle a format: :html request to /frontend/posts. Note: If you specify a custom path, you must also update the rootURL in frontend/config/environment.js. See Mounting multiple Ember applications for more information.
  • controller - Defaults to "ember_cli/ember"
  • action - Defaults to "index"

Finally, install your Ember application's dependencies:

$ rake ember:install

Boot your Rails application, navigate to "/", and view your EmberCLI application!


EmberCLI Rails exposes several useful rake tasks.


Install the Ember applications' dependencies.


Compile the Ember applications.


Execute Ember's test suite.

If you're using Rake to run the test suite, make sure to configure your test task to depend on ember:test.

For example, to configure a bare rake command to run both RSpec and Ember test suites, configure the default task to depend on both spec and ember:test.

task default: [:spec, "ember:test"]


When Rails is running in production mode, EmberCLI-Rails stops doing runtime compilation. Instead, configured apps are built during rake assets:precompile. This keeps things quick for end users, and extends the normal Rails asset building process.

Configuration information, including instructions for Heroku and Capistrano, can be found below.


In production environments, assets should be served over a Content Delivery Network.

Configuring an ember-cli-rails application to serve Ember's assets over a CDN is very similar to configuring an EmberCLI application to serve assets over a CDN:

var app = new EmberApp({
  fingerprint: {
    prepend: ''

If you're serving the Ember application from a path other than "/", the prepend URL must end with the mounted path:

var app = new EmberApp({
  fingerprint: {
    // for an Ember application mounted to `/admin_panel/`
    prepend: '',

As long as your CDN is configured to pull from your Rails application , your assets will be served over the CDN.

Deployment Strategies

By default, EmberCLI-Rails uses a file-based deployment strategy that depends on the output of ember build.

Using this deployment strategy, Rails will serve the index.html file and other assets that ember build produces.

These EmberCLI-generated assets are served with the same Cache-Control headers as Rails' other static files:

# config/environments/production.rb
Rails.application.configure do
  # serve static files with cache headers set to expire in 1 year
  config.static_cache_control = "public, max-age=31622400"

If you need to override this behavior (for instance, if you're using ember-cli-deploy's "Lightning Fast Deployment" strategy in production), you can specify the strategy's class in the initializer:

EmberCli.configure do |config| :frontend, deploy: { production: EmberCli::Deploy::Redis }

This example configures the frontend Ember application to retrieve the index's HTML from an ember-cli-deploy-redis -populated Redis entry using the ember-cli-rails-deploy-redis gem.

If you're deploying HTML with a custom strategy in development or test, disable EmberCLI-Rails' build step by setting ENV["SKIP_EMBER"] = true.


Specifying a deployment strategy is only supported for applications that use the mount_ember_app and render_ember_app helpers.


To configure your EmberCLI-Rails applications for Heroku:

  1. Execute rails generate ember:heroku.
  2. Commit the newly generated files.
  3. Add the NodeJS buildpack and configure NPM to include the bower dependency's executable file (if your build process requires bower).
$ heroku buildpacks:clear
$ heroku buildpacks:add --index 1 heroku/nodejs
$ heroku buildpacks:add --index 2 heroku/ruby
$ heroku config:unset SKIP_EMBER

You are ready to deploy:

$ git push heroku master

EmberCLI compilation happens at deploy-time, triggered by the asset:precompile rake task.

NOTE Run the generator each time you introduce additional EmberCLI applications into the project.

Slug size

Heroku slug size is limited. The build process creates artifacts that are not necessary for the server to run, but are included in the deployed Heroku slug.

Omitting these build assets can dramatically reduce slug size.

A build-pack solution for this is discussed in Issue #491.


EmberCLI-Rails executes both npm install and bower install during EmberCLI's compilation, triggered by the asset:precompile rake task.

The npm and bower executables are required to be defined in the deployment SSH session's $PATH. It is not sufficient to modify the session's $PATH in a .bash_profile.

To resolve this issue, prepend the Node installation's bin directory to the target system's $PATH:


set :default_env, {
  "PATH" => "/home/deploy/.nvm/versions/node/v4.2.1/bin:$PATH"

The system in this example is using nvm to configure the node version. If you're not using nvm, make sure the string you prepend to the $PATH variable contains the directory or directories that contain the bower and npm executables.

For faster deployments

Place the following in your deploy/<environment>.rb

set :linked_dirs, %w{<ember-app-name>/node_modules <ember-app-name>/bower_components}

to avoid rebuilding all the node modules and bower components with every deploy. Replace <ember-app-name> with the name of your ember app (default is frontend).


By default, routes defined by ember_app will be rendered with the internal EmberCli::EmberController.

Overriding the view

The EmberCli::EmberController renders the Ember application's index.html and injects the Rails-generated CSRF tags into the <head>.

To customize the view, create app/views/ember_cli/ember/index.html.erb:

<%= render_ember_app ember_app do |head| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

The ember_app helper is available within the EmberCli::EmberController's view, and refers to the name of the current EmberCLI application.

To inject the EmberCLI generated index.html, use the render_ember_app helper in your view:

<!-- app/views/application/index.html.erb -->
<%= render_ember_app :frontend do |head, body| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>

  <% body.append do %>
    <%= render partial: "my-analytics" %>
  <% end %>
<% end %>

The body block argument and the corresponding call to body.append in the example are both optional, and can be omitted.

Serving Rails-generated CSS

For more information on how to work with EmberCLI-generated stylesheets, refer to the Stylesheets section. EmberCLI-generated CSS will be embedded in the response's HTML document by default.

To serve assets generated and served by Rails, inject them into the document's <head>:

<%= render_ember_app :frontend do |head| %>
  <% head.append do %>
    <%= stylesheet_link_tag "application" %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

There are no technical limitations to sharing assets between the Ember client and the Rails server, but picking one or the other might simplify the project's organization.

Sharing code during asset compilation is not possible.

For example, Ember's SCSS files cannot use @import directives referencing Rails' SCSS modules.

Overriding the controller

To override this behavior, you can specify [any of Rails' routing options] route-options.

For the sake of this example, override the controller and action options:

# config/routes.rb

Rails.application.routes.draw do
  mount_ember_app :frontend, to: "/", controller: "application", action: "index"

When serving the EmberCLI generated index.html with the render_ember_app helper, make sure the controller's layout is disabled, as EmberCLI generates a fully-formed HTML document:

# app/controllers/application.rb
class ApplicationController < ActionController::Base
  def index
    render layout: false

Rendering the EmberCLI generated JS and CSS

Rendering EmberCLI applications with render_ember_app is the recommended, actively supported method of serving EmberCLI applications.

However, for the sake of backwards compatibility, ember-cli-rails supports injecting the EmberCLI-generated assets into an existing Rails layout.

Following the example above, configure the mounted EmberCLI application to be served by a custom controller (ApplicationController, in this case).

In the corresponding view, use the asset helpers:

<%= include_ember_script_tags :frontend %>
<%= include_ember_stylesheet_tags :frontend %>

Mounting multiple Ember applications

Rendering Ember applications to paths other than / requires additional configuration.

Consider a scenario where you had Ember applications named frontend and admin_panel, served from / and /admin_panel respectively.

First, specify the Ember applications in the initializer:

EmberCli.configure do |c| :frontend :admin_panel, path: "path/to/admin_ember_app"

Next, mount the applications alongside the rest of Rails' routes. Note that admin_panel route is added before the frontend route because it's more specific:

# /config/routes.rb
Rails.application.routes.draw do
  mount_ember_app :admin_panel, to: "/admin_panel"
  mount_ember_app :frontend, to: "/"

Then set each Ember application's rootURL to the mount point:

// frontend/config/environment.js

module.exports = function(environment) {
  var ENV = {
    modulePrefix: 'frontend',
    environment: environment,
    rootURL: '/',
    // ...

// path/to/admin_ember_app/config/environment.js

module.exports = function(environment) {
  var ENV = {
    modulePrefix: 'admin_panel',
    environment: environment,
    rootURL: '/admin_panel',  // originally '/'
    // ...

Finally, configure EmberCLI's fingerprinting to prepend the mount point to the application's assets:

// frontend/ember-cli-build.js

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    fingerprint: {
      // matches the `/` mount point
      prepend: '',

// path/to/admin_ember_app/ember-cli-build.js

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    fingerprint: {
      // matches the `/admin_panel` mount point
      prepend: '',

When injecting the EmberCLI-generated assets with the include_ember_script_tags and include_ember_stylesheet_tags helpers to a path other than "/", a <base> tag must also be injected with a corresponding href value:

<base href="/">
<%= include_ember_script_tags :frontend %>
<%= include_ember_stylesheet_tags :frontend %>

<base href="/admin_panel/">
<%= include_ember_script_tags :admin_panel %>
<%= include_ember_stylesheet_tags :admin_panel %>

If you're using the include_ember style helpers with a single-page Ember application that defers routing to the Rails application, insert a call to mount_ember_assets at the bottom of your routes file to serve the EmberCLI-generated assets:

# config/routes.rb
Rails.application.routes.draw do
  mount_ember_assets :frontend, to: "/"

CSRF Tokens

Your Rails controllers, by default, expect a valid authenticity token to be submitted along with non-GET requests.

Without the authenticity token, requests will respond with 422 Unprocessable Entity errors (specifically ActionController::InvalidAuthenticityToken).

To add the necessary tokens to requests, inject the csrf_meta_tags into the template:

<!-- app/views/application/index.html.erb -->
<%= render_ember_app :frontend do |head| %>
  <% head.append do %>
    <%= csrf_meta_tags %>
  <% end %>
<% end %>

The default EmberCli::EmberController and the default view handle behave like this by default.

If an Ember application is mounted with another controller, it should append the CSRF tags to its view's <head>.

ember-cli-rails-addon configures your Ember application to make HTTP requests with the injected CSRF tokens in the X-CSRF-TOKEN header.

Serving from multi-process servers in development

If you're using a multi-process server (Puma, Unicorn, etc.) in development, make sure it's configured to run a single worker process.

Without restricting the server to a single process, it is possible for multiple EmberCLI runners to clobber each others' work.


If set on the environment, SKIP_EMBER will configure ember-cli-rails to skip the build step entirely. This is useful if you're using an alternative deployment strategy in the test or development environment. By default, ember-cli-rails will skip the build step in production-like environments.


If set on the environment, the value of EMBER_ENV will be passed to the ember process as the value of the --environment flag.

If EMBER_ENV is unspecified, the current Rails environment will be passed to the ember process, with the exception of non-standard Rails environments, which will be replaced with production.


While being managed by EmberCLI Rails, EmberCLI process will have access to the RAILS_ENV environment variable. This can be helpful to detect the Rails environment from within the EmberCLI process.

This can be useful to determine whether or not EmberCLI is running in its own standalone process or being managed by Rails.

For example, to enable ember-cli-mirage API responses in development while being run outside of Rails (while run by ember serve), check for the absence of the RAILS_ENV environment variable:

// config/environment.js
if (environment === 'development') {
  ENV['ember-cli-mirage'] = {
    enabled: typeof process.env.RAILS_ENV === 'undefined',

RAILS_ENV will be absent in production builds.

EmberCLI support

This project supports:

  • EmberCLI versions >= 1.13.13

Ruby and Rails support

This project supports:

  • Ruby versions >= 2.5.0
  • Rails versions >=5.2.x.

To learn more about supported versions and upgrades, read the upgrading guide.


See the CONTRIBUTING document. Thank you, contributors!


Open source templates are Copyright (c) 2015 thoughtbot, inc. It contains free software that may be redistributed under the terms specified in the LICENSE file.


ember-cli-rails was originally created by Pavel Pravosud and Jonathan Jackson.

ember-cli-rails is maintained by Sean Doyle and Jonathan Jackson.


ember-cli-rails is maintained and funded by thoughtbot, inc. The names and logos for thoughtbot are trademarks of thoughtbot, inc.

We love open source software! See our other projects or hire us to help build your product.