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This project is no longer maintained. I recommend that you use a different tool. I don't have a specific one to suggest, having never used any, but PurifyCSS and UnCSS both seem to be actively worked on.


Deadweight is a CSS coverage tool. Given a set of stylesheets and a set of URLs, it determines which selectors are actually used and reports which can be "safely" deleted.


Ryan Bates has worked his magic once again. Head over here for an excellent introduction to Deadweight.

How to Install It

$ gem install deadweight

How to Use It

There are multiple ways to use Deadweight. It's designed to be completely agnostic of whatever framework (or indeed language) your website is built on, but optimised for Ruby and Rails.

Run it From the Command Line

$ deadweight -s styles.css -s ie.css index.html about.html
$ deadweight -s
$ deadweight --root -s '/templates/2009/css.php?p=mac' / /everfresh /about

Integrate it With Your Integration Tests

Deadweight can hijack your Rails integration tests (both the spartan Test::Unit type and the refreshing Cucumber variety), capturing every page that is returned by your app during testing and saving you the trouble of manually specifying a ton of URLs and login processses.

First, put this in your Gemfile:

group :test do
  gem 'colored'
  gem 'deadweight', :require => 'deadweight/hijack/rails'

Then, run your integration tests with the environment variable DEADWEIGHT set to true:

rake test DEADWEIGHT=true
rake cucumber DEADWEIGHT=true

Let me know how it goes. It's not terribly customisable at the moment (you can't specify what exact stylesheets to look at, or what selectors to ignore). I'm looking for your feedback on how you'd like to be able to do that.

Rake Task

# lib/tasks/deadweight.rake

require 'deadweight' do |dw|
  dw.stylesheets = ["/stylesheets/style.css"]
  dw.pages = ["/", "/page/1", "/about"]

Running rake deadweight will output all unused rules, one per line. Note that it looks at http://localhost:3000 by default, so you'll need to have script/server (or whatever your server command looks like) running.

Call it Directly from Ruby

require 'deadweight'

dw =
dw.stylesheets = ["/stylesheets/style.css"]
dw.pages = ["/", "/page/1", "/about"]

Pipe In CSS Rules from STDIN

$ cat styles.css | deadweight index.html

Use it as an HTTP Proxy

$ deadweight -l deadweight.log -s styles.css -w -P

Setting the Root URL

By default, Deadweight uses http://localhost:3000 as the base URL for all paths. To change it, set root:

dw.root = ""      # staging server
dw.root = "" # urls can have paths in
dw.root = "/path/to/some/html"              # local paths work too

What About Stuff Added by Javascript?

Deadweight is completely ignorant of classes, IDs or tags added by your Javascript layer, but you can filter them out by setting ignore_selectors:

dw.ignore_selectors = /hover|lightbox|superimposed_kittens/

The command-line tool also has basic support for Lyndon with the -L flag, which simply pipes all HTML through the lyndon executable to execute any embedded or linked JS.

You Can Use Mechanize for Complex Stuff

Set mechanize to true and add a Proc to pages (rather than a String), and Deadweight will execute it using Mechanize:

dw.mechanize = true

# go through the login form to get to a protected URL
dw.pages << proc {
  form =
  form.username = 'username'
  form.password = 'password'

# use HTTP basic auth
dw.pages << proc {
  agent.auth('username', 'password')

The agent method returns the Mechanize instance. The fetch method is a wrapper around agent.get that will abort in the event of an HTTP error status.

If You Install colored, It'll Look Nicer

gem install colored


Copyright (c) 2009 Aanand Prasad. See LICENSE for details.