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Use npm as part of your Rails asset pipeline
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Use npm as part of your Rails asset pipeline

npm-pipeline-rails allows you to use any toolchain to build your asset files in Rails 4.2+. This allows you to:

See § How it Works for an explanation of the diagram above.

⚠️ Notice ⚠️

Rails 5.1 will be adding official support for Webpack via webpacker. In contrast, npm-pipeline-rails is far less opinionated and more flexible than webpacker, but expect better support from using Rails's official integration.


Add this line below to your Gemfile. After that, proceed with an automated or manual setup.

gem 'npm-pipeline-rails'

Automated setup

Use the generators for your preferred build tool:

  • Brunch - ./bin/rails generate npm_pipeline:brunch
  • Gulp - ./bin/rails generate npm_pipeline:gulp
  • Webpack - ./bin/rails generate npm_pipeline:webpack

Manual setup

  • Put together a setup with Brunch, Broccoli, Gulp, Webpack or any other tool. It should:
    • Take source files from app/webpack/
    • Render CSS to vendor/assets/stylesheets/webpack/
    • Render JS to vendor/assets/javascripts/webpack/
    • (Replace webpack with whatever build tool you use.)
  • Create a package.json with start and build scripts to point to this setup. (See example)
    • start - Configure this script to run a development file watcher.
    • build - Configure this script to run a production compiler.
  • Add your expected compiled assets to .gitignore.

Set up support for tests

If you're using continuous integration for your tests, configure it to run this before your tests:

npm run build

For tests running in your development machine, ensure that asset files are available when running your tests. This means starting your dev server at least once before running tests, or invoking npm run build manually.

Disable some gems

You may also want to disable some gems, depending on your set up:

  • Disable uglifyjs if you already do minification in your npm tool.
  • Disable autoprefixer-rails if you already do autoprefixing in your npm tool.
  • Disable sprockets-es6 if you already do ES6 compiling in your npm tool.
  • and so on...


When deploying to Heroku, use Node.js and Ruby buildpacks together. See: Using Multiple Buildpacks for an App (

$ heroku buildpacks:set heroku/ruby
$ heroku buildpacks:add --index 1 heroku/nodejs

Buildpack added. Next release on my-app-name will use:
  1. heroku/nodejs
  2. heroku/ruby

It's recommended to turn off config.npm.install_on_asset_precompile to make deployments faster; see § Configuration.


npm-pipeline-rails provides these configuration options below. Put them inside config/application.rb (not in an initializer!).

# These are defaults; in most cases, you don't need to configure anything.

Rails.application.configure do
  # Enables npm_pipeline_rails's invocation of `watch` commands. (v1.5.0+)
  # If `true`, watch commands will be ran alongside Rails's server.
  # Defaults to true in development.
  config.npm.enable_watch = Rails.env.development?

  # Command to install dependencies
  config.npm.install = ['npm install']

  # Command to build production assets = ['npm run build']

  # Command to start a file watcher = ['npm run start']

  # The commands are arrays; you may add more commands as needed: = [
    'npm run webpack:start',
    'npm run brunch:start'

  # If 'true', runs 'npm install' on 'rake assets:precompile'. (v1.6.0+)
  # If you disable this, you'll need to run `npm install` yourself.
  # This is generally desired, but you may set this to false when
  # deploying to Heroku to speed things up.
  config.npm.install_on_asset_precompile = true

  # If 'true', runs 'npm install' on 'rails server'. (v1.7.0+)
  # If you disable this, you'll need to run `npm install` yourself.
  config.npm.install_on_rails_server = true

How it works

npm-pipeline-rails allows you to hook certain commands, usually npm scripts, during the Rails app lifecycle. It assumes that your tool will build plain JS and CSS files into vendor/assets, allowing it to be picked up by Rails's asset pipeline.

It does not replace the Rails asset pipeline, but rather it works with it. The files you build with your npm pipeline will be available as regular files in the Rails asset pipeline.

In development

When starting a Rails development server (bundle exec rails s), it runs the install command. After that, it starts a background process that runs your watch command.

In production

When running rake assets:precompile, it will first run the install command then the build command.

More info

Consult railtie.rb for the actual code that makes all these happen.


To use Yarn instead of npm, change config.npm.install as seen below in config/application.rb. See § Configuration for more details.

Rails.application.configure do
  # ...

  config.npm.install = ['yarn']

Skipping Rails asset pipeline

The recommended setup renders files to vendor/assets/stylesheets/webpack/ and vendor/assets/javascripts/webpack/. (Replace webpack with whatever build tool you use.) You may opt to output to public/assets/stylesheets/ and public/assets/javascripts/ instead.

This is not recommended since you will miss out on automatic asset fingerprinting, among other nice integrations.

If you do this, you will need to run npm run build as part of your deploy script and CI test script.


Rails's asset pipeline was a great step forward for Rails 3. For today's requirements however, it doesn't always come with all the tools you need. npm-pipeline-rails lets you outsource asset building complexities to Node.js-based tools.

Read more →

Also see


npm-pipeline-rails © 2016+, Rico Sta. Cruz. Released under the MIT License.
Authored and maintained by Rico Sta. Cruz with help from contributors (list).  ·  GitHub @rstacruz  ·  Twitter @rstacruz

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