csso-rails: Stylesheet Optimizer (CSSO) for Rails Asset pipeline

Ruby adapter for github.com/css/csso.

CSSO does structure-optimization for CSS.
CSS is usually reduced more than in half in uncompressed and around 15% in gzipped.

A Real-World Example

A living rails application CSS – some written in less, some handwritten):

	Original	sass	yui 2.4.7	csso	% of original
Plain	129497	107006	60758	60874	47%
GZipped	14046	12047	10558	10472	74%

Very close to yui compressor, wining in gzipped (you’re using nginx mod\_gzip_static, don’t you?)

A more hard example – twitter bootstrap.css, already minified:

	Original	lessc	yui 2.4.7	csso	% of original
Plain	81443	71520	68755	67679	83%
GZipped	12384	11633	11652	11477	92%

Please note than benchmark was taken in summer of 2012, since then things may have changed.

Usage

In Rails 3.1+

Add gem 'csso-rails' to your gemfile, and that’s it!
(also you may want to add some javascript runtime for ExecJS to pick up, like gem 'therubyracer')

Upon including it becomes the default compressor even if sass is included too.
More explicit way – set in config/environment/production.rb:

config.assets.css_compressor = :csso

Sprockets

If you use Sprockets without Rails:

require 'csso'
Csso.install(sprockets_env)

In Plain Ruby

require 'csso'
puts Csso.optimize("a{ color: #FF0000; }") # produces "a{color:red}"

In maniac mode (Csso.optimize(css, true), default for pipeline) CSS is processed several times until it stops getting lighter (there’re cases when original csso does not do all optimizations for no reason).

In Command Line

ruby_csso non_optimized.css > optimized.css

MIT-License

Original CSSO code - Copyright © 2011 by Sergey Kryzhanovsky.

ruby gem - Copyright© 2012 Vasily Fedoseyev

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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