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Hey fellow Rails developers, please read!

Want to use rack-zippy with a Rails v4.2 or greater app?
Its recommended you don't! Rails 4.2+ now supports serving gzipped files directly so there's no need for rack-zippy in Rails 4.2+ apps.

Want to use rack-zippy with a Rails v4.1 or less app?
You'll need to use v3.0 of rack-zippy, see the README here:


rack-zippy v4+ is a Rack middleware for serving .gz files in Rack apps that are not Rails 4.2+ apps. (If you need to use rack-zippy in a Rails <= 4.1 app, then use v3.0 of rack-zippy, see README here:

rack-zippy has convenient directory request handling:

  • Requests for / and /index respond with public/index.html if present
  • Requests for /foo/ and /foo respond with first file present out of public/foo.html, public/foo/index.html (Same behaviour for subdirectories)

rack-zippy decorates actionpack's ActionDispatch::Static middleware for non-Rails Rack apps to provide rack-zippy's own choice of caching headers and whitelisting of permitted static file extensions. (As an alternative to rack-zippy, you can use actionpack's ActionDispatch::Static directly without rack-zippy.)

Installation in Rack app (that isn’t a Rails app)

Add this line to your application's Gemfile:

gem 'rack-zippy'

And then execute:

$ bundle


require 'rack-zippy'

# Set asset_root to an absolute or relative path to the directory holding your asset files
# e.g. '/path/to/my/apps/static-assets' or 'public'
asset_root = '/path/to/my/apps/public'
use Rack::Zippy::AssetServer, asset_root


Follow the installation instructions above and rack-zippy will serve any static assets, including gzipped assets, from your application's public/ directory and will respond with sensible caching headers.



max_age_fallback, is an integer value in seconds that should be used as the max_age fallback for files served by rack-zippy that live outside the /assets subdirectory and aren't /favicon.ico.

A typical use for max_age_fallback is to define how long the cache lifetime for static HTML files served by rack-zippy should be. For one of my sites I have this set to 15 minutes:

max_age_in_secs = 15*60 # 15 mins = 900 secs
use Rack::Zippy::AssetServer, asset_root, max_age_fallback: max_age_in_secs

Any files given the max_age_fallback would have the following Cache-Control header:

Cache-Control: public, max-age=900


Supported Extensions Whitelist

rack-zippy handles only files with whitelisted extensions. Default extensions are stored in the static_extensions array with an entry for each of these: css js html htm txt ico png jpg jpeg gif pdf svg zip gz eps psd ai woff woff2 ttf eot otf swf

You can modify this list to support other extensions by appending the lowercased file extension to the static_extensions array:

Rack::Zippy.configure do |config|
  # Add support for the given extensions:
  config.static_extensions.push('map', 'csv', 'xls', 'rtf', ...EXTENSIONS TO ADD...)

It is not recommended, however if you use rack-zippy 4.0+ with a Rails 4.2+ app, you can skip the rack-zippy rails version check and log output. Put the following in an initializer:

# config/initializers/zippy.rb
Rack::Zippy::Railtie.skip_version_check = true


NameError: uninitialized constant Rack::Zippy
  • Check Gemfile doesn't limit rack-zippy to a subset of environment groups
  • Run bundle install
  • Check Gemfile.lock contains an entry for rack-zippy
  • Ensure require 'rack-zippy' is present near the top of


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Run tests (rake test)
  4. Commit your changes (git commit -am 'Add some feature')
  5. Push to the branch (git push origin my-new-feature)
  6. Create new Pull Request

Optional for contributors

To try a local branch of rack-zippy out as the gem dependency in a local app, configure bundler with a local gem override as follows:

In your-app/Gemfile: edit the rack-zippy dependency to the following:

# The branch your-local-branch-name **must** exist otherwise bundler will shout obscenities at you
gem 'rack-zippy', :github => 'eliotsykes/rack-zippy', :branch => 'your-local-branch-name'

At the command line, inside your-app, configure bundler to set a local git repo to override the one we specified in the previous step for rack-zippy:

$> bundle config --local local.rack-zippy /path/to/your/local/rack-zippy

Now when you run your-app with bundle exec, the rack-zippy gem dependency will resolve to /path/to/your/local/rack-zippy.

Cleanup time! When you’re finished testing, delete the local override and set your Gemfile dependency back to the original:

# At the command line:
$> bundle config --delete local.rack-zippy

# In your-app/Gemfile change rack-zippy dependency to this (or similar):
gem 'rack-zippy', '~> 9.8.7' # Replace 9.8.7 with the rack-zippy release version you want to use.

How to Run a Single Test

# Single test file
ruby -Ilib:test test/assert_server_test.rb

# Single test method
ruby -Ilib:test test/assert_server_test.rb --name test_serves_static_file_as_directory

# Test methods matching a regex
ruby -Ilib:test test/assert_server_test.rb --name /serves_static/


Releasing a new gem

  1. Update pre-release version to the release version in lib/rack-zippy/version.rb, e.g. 1.0.1.pre becomes 1.0.1
  2. Update version and date. Update Contributors in
  3. Tests pass? (rake test)
  4. Commit and push changes to origin.
  5. Build the gem (rake build)
  6. Release on (rake release)
  7. Update version to the next pre-release version in lib/rack-zippy/version.rb, e.g. 1.0.1 becomes 1.0.2.pre.
  8. Add new heading to CHANGELOG for the next pre-release
  9. Commit and push the updated lib/rack-zippy/version.rb and CHANGELOG files.


Rack middleware for serving gzip files







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