Sprockets Rails

Provides Sprockets implementation for Rails 4.x (and beyond) Asset Pipeline.


gem 'sprockets-rails', :require => 'sprockets/railtie'

Or alternatively require 'sprockets/railtie' in your config/application.rb if you have Bundler auto-require disabled.


Rake task

rake assets:precompile

Deployment task that compiles any assets listed in config.assets.precompile to public/assets.

rake assets:clean

Only removes old assets (keeps the most recent 3 copies) from public/assets. Useful when doing rolling deploys that may still be serving old assets while the new ones are being compiled.

rake assets:clobber

Nuke public/assets and clear the Sprockets file system cache.


If the basic tasks don't do all that you need, it's straight forward to redefine them and replace them with something more specific to your app.

You can also redefine the task with the built in task generator.

require 'sprockets/rails/task'
Sprockets::Rails::Task.new do |t|
  t.environment = lambda { Rails.application.assets }
  t.assets = %w( application.js application.css )
  t.keep = 5

Each asset task will invoke assets:environment first. By default this loads the Rails environment. You can override this task to add or remove dependencies for your specific compilation environment.

Also see Sprockets::Rails::Task and Rake::SprocketsTask.

Initializer options


Add additional assets to compile on deploy. Defaults to application.js, application.css and any other non-js/css file under app/assets.


Add additional load paths to this Array. Rails includes app/assets and vendor/assets for you already. Plugins might want to add their custom paths to to this.


Set a custom cache buster string. Changing it will cause all assets to recompile on the next build.

config.assets.version = 'v1'
# after installing a new plugin, change loads paths
config.assets.version = 'v2'


Defaults to /assets. Changes the directory to compile assets to.


Link to undigest asset filenames. This option will eventually go away. Unless when compile is disabled.


Enable expanded asset debugging mode. Individual files will be served to make referencing filenames in the web console easier. This feature will eventually be deprecated and replaced by Source Maps in Sprockets 3.x.


Enables Sprockets compile environment. If disabled, Rails.application.assets will be unavailable to any ActionView helpers. View helpers will depend on assets being precompiled to public/assets in order to link to them. You can still access the environment by directly calling Rails.application.assets.


Invokes block with environment when the environment is initialized. Allows direct access to the environment instance and lets you lazily load libraries only needed for asset compiling.

config.assets.configure do |env|
  env.js_compressor  = :uglify # or :closure, :yui
  env.css_compressor = :sass   # or :yui

  require 'my_processor'
  env.register_preprocessor 'application/javascript', MyProcessor

  env.logger = Rails.logger

  env.cache = ActiveSupport::Cache::FileStore.new("tmp/cache/assets")

Complementary plugins

The following plugins provide some extras for the Sprockets Asset Pipeline.

NOTE That these plugins are optional. The core coffee-script, sass, less, uglify, (any many more) features are built into Sprockets itself. Many of these plugins only provide generators and extra helpers. You can probably get by without them.

Changes from Rails 3.x

  • Only compiles digest filenames. Static non-digest assets should simply live in public/.
  • Unmanaged asset paths and urls fallback to linking to public/. This should make it easier to work with both compiled assets and simple static assets. As a side effect, there will never be any "asset not precompiled errors" when linking to missing assets. They will just link to a public file which may or may not exist.
  • JS and CSS compressors must be explicitly set. Magic detection has been removed to avoid loading compressors in environments where you want to avoid loading any of the asset libraries. Assign config.assets.js_compressor = :uglify or config.assets.css_compressor = :sass for the standard compressors.
  • The manifest file is now in a JSON format. Since it lives in public/ by default, the initial filename is also randomized to obfuscate public access to the resource.
  • Two cleanup tasks. rake assets:clean is now a safe cleanup that only removes older assets that are no longer used. While rake assets:clobber nukes the entire public/assets directory and clears your filesystem cache. The clean task allows for rolling deploys that may still be linking to an old asset while the new assets are being built.


Usual bundler workflow.

$ git clone https://github.com/rails/sprockets-rails.git
$ cd sprockets-rails/
$ bundle install
$ bundle exec rake test

Build Status


sprockets-rails 2.x will primarily target sprockets 2.x. And future versions will target the corresponding sprockets release line.

The minor and patch version will be updated according to semver.

  • Any new APIs or config options that don't break compatibility will be in a minor release
  • Any time the sprockets depedency is bumped, there will be a new minor release
  • Simple bug fixes will be patch releases


Copyright © 2012 Joshua Peek.

Released under the MIT license. See LICENSE for details.