CloudFront AssetHost

Easy deployment of your assets on CloudFront or S3. When enabled in production, your assets will be served from CloudFront/S3 which will result in a speedier front-end.


Hosting your assets on CloudFront ensures minimum latency for all your visitors. But deploying your assets requires some additional management that this gem provides.


The best way to expire your assets on CloudFront is to upload the asset to a new unique url. The gem will calculate the MD5-hash of the asset and incorporate that into the URL.

Efficient uploading

By using the MD5-hash we can easily determine which assets aren't uploaded yet. This speeds up the deployment considerably.

Compressed assets

CloudFront will not serve compressed assets automatically. To counter this, the gem will upload gzipped javascripts and stylesheets and serve them when the user-agent supports it.


gem install cloudfront_asset_host

Add the gem to your environment.rb or Gemfile.


The gem relies on the gzip utility. Make sure it is available locally.


Make sure your s3-credentials are stored in config/s3.yml like this:

access_key_id: 'access_key'
secret_access_key: 'secret'

or with environment specified:

  access_key_id: 'access_key'
  secret_access_key: 'secret'

Create an initializer to configure the plugin config/initializers/cloudfront_asset_host.rb

# Simple configuration
CloudfrontAssetHost.configure do |config|
  config.bucket = "bucketname" # required
  config.enabled = true if Rails.env.production? # only enable in production

# Extended configuration
CloudfrontAssetHost.configure do |config|
  config.bucket       = "bucketname"        # required
  config.cname        = "" # cname configured for your distribution or bucket

  config.key_prefix   = "app/"              # prefix for paths
  config.plain_prefix = ""                  # prefix for paths to uncompressed files

  config.asset_dirs   = %w(images flash)    # specify directories to be uploaded
  config.exclude_pattern = /pdf/            # exclude matching assets from uploading

  # s3 configuration
  config.s3_config    = "path/to/s3.yml"    # Alternative location of your s3-config file
  config.s3_logging   = true                # enable logging for this bucket

  # gzip related configuration
  config.gzip = true                      # enable gzipped assets (defaults to true)
  config.gzip_extensions = ['js', 'css']  # only gzip javascript or css (defaults to %w(js css))
  config.gzip_prefix = "gz"               # prefix for gzipped bucket (defaults to "gz")

  config.enabled = true if Rails.env.production? # only enable in production

The cname option also accepts a Proc or String with the %d parameter (e.g. "" for multiple hosts).


Uploading your assets

Run CloudfrontAssetHost::Uploader.upload!(:verbose => true, :dryrun => false) before your deployment. Put it for example in your Rakefile or Capistrano-recipe. Verbose output will include information about which keys are being uploaded. Enabling dryrun will skip the actual upload if you're just interested to see what will be uploaded.


If the plugin is enabled. Rails' internal asset_host and asset_id functionality will be overridden to point to the location of the assets on Cloudfront.

Other plugins

When using in combination with SASS and/or asset_packager it is recommended to generate the css files and package your assets before uploading them to Cloudfront. For example, call Sass::Plugin.update_stylesheets and Synthesis::AssetPackage.build_all first.


  • 1.1

    • New features:
      • Add support for CNAME-interpolation [wpeterson]
      • Add ability to specify an exclude regex for CDN content [wpeterson]
      • Configure directories to upload through CloudfrontAssetHost.asset_dirs [wpeterson]
      • CloudfrontAssetHost.cname accepts Proc [foresth]
      • Rewrite all css-files when some images are modified [foresth]
      • Enable S3-logging with CloudfrontAssetHost.s3_loggin (defaults to false) [foresth]
      • Ability to insert prefix to paths to uncompressed files [foresth]
      • Ability to define environment specific credentials in s3.yml [foresth]
    • Fixes and improvements:
      • Strip query-parameters from image-urls in CSS [wpeterson]
      • Use Digest::MD5 as md5-implementation [wpeterson, mattdb, foresth]
      • Fix bug working with paths with spaces [caleb]
  • 1.0.2

    • Fix bug serving gzipped-assets to IE
  • 1.0.1

    • First release


Feel free to fork the project and send pull requests.


Thanks to these people who contributed patches:


Tested on Rails 2.3.5 with SASS and AssetPackager plugins

Created at Wakoopa

Copyright (c) 2010 Menno van der Sman, released under the MIT license