Smurf is a Rails plugin that does Javascript and CSS minification the way you would expect. See, with Rails 2.x we got this cool new :cache option on javascript_include_tag and stylesheet_link_tag, but no option for minifying the cached file(s).

Smurf ends that. Smurf - if installed and when caching is enabled for the environment - will nab the concatenated file content from Rails just before it saves it and minifies the content using either JSmin or a custom CSS compressor.

Some cool things about Smurf, which also allude to the reasons I wrote it:

  • Smurf will only run when Rails needs to cache new files
  • It will never run on its own
  • It requires absolutely no configuration
  • Other than installing it, you don't need to do anything
  • It just gets out of your way

Smurf will work with most versions of Rails 2.3.x and above; including Rails 3.0.0.


It's really an adaptation of Uladzislau Latynski's jsmin.rb port of Douglas Crockford's jsmin.c library.

Smurf CSS Compressor

The following are the rules I applied, gathered from various perusals around the Internet*s*

  1. Replace consecutive whitespace characters with a single space
  2. Remove whitespace around opening brackets
  3. Remove whitespace in front of closing brackets
  4. Remove the semi-colon just before the closing bracket
  5. Remove comments between /* ... */ - this could be a problem (esp. for CSS hacks)
  6. Remove spaces around ;, :, and , characters
  7. Ensure whitespace between closing brackets and periods
  8. Preserves [conditional comments](\).aspx) in IE (ex: /*@cc_on document.write("this will only write in IE") @*/)


You install Smurf as a gem:

sudo gem install smurf

Because this latest version is intended to work with Rails 3 and above, you'll need to update your Gemfile ad add:

gem 'smurf'

Then, wherever you define javascript_include_tag or stylesheet_link_tag, make sure to add the standard :cache => true or :cache => 'some_bundle' options.

Also make sure to at least have this setting in your production.rb:

config.perform_caching = true

Small suggestion

bcarpenter reminded all of us that Rails will generate real files if you set config.action_controller.perform_caching to true. If you happen to do this while developing your fantastic Rails app you may also accidentally commit them to your development repository. This is not what you want as it can send you and your awesome developer friends down the wrong rabbit hole ... and then when you figure out the problem you may be understandably and misguidedly pissed at Smurf :)

bcarpenter didn't seem too mad since he reached out to me (whew!) and suggested I add a little comment about making sure to ignore the generated cache files/directories in your SCM of choice. If you happen to be using git, be sure to do something to the effect of the following in your .gitignore file:





If you want to play around with different versions, you'll need to update the Gemfile version of rails. While Smurf itself should work as is with Rails 3 and Rails 2.3.x, the test setup is different enough between 3 and 2.3.x that I can't make guarantees. Currently tests require Rails 3 to be run successfully. If you need a previous version of smurf, look for the appropriate tag in the source code.


Author: Justin Knowlden [email protected]

Contributions from: Lance Ivy, Scott White, Daniel Schierbeck, Paul Hepworth

See MIT-LICENSE for licensing information