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Note: This README details the 3.x version of Roadie. You might be using 2.x, which is much older and only for Rails.

Making HTML emails comfortable for the Ruby rockstars

Roadie tries to make sending HTML emails a little less painful by inlining stylesheets and rewriting relative URLs for you inside your emails.

How does it work?

Email clients have bad support for stylesheets, and some of them blocks stylesheets from downloading. The easiest way to handle this is to work with inline styles (style="..."), but that is error prone and hard to work with as you cannot use classes and/or reuse styling over your HTML.

This gem makes this easier by automatically inlining stylesheets into the document. You give Roadie your CSS, or let it find it by itself from the <link> and <style> tags in the markup, and it will go through all of the selectors assigning the styles to the matching elements. Careful attention has been put into selectors being applied in the correct order, so it should behave just like in the browser.

"Dynamic" selectors (:hover, :visited, :focus, etc.), or selectors not understood by Nokogiri will be inlined into a single <style> element for those email clients that support it. This changes specificity a great deal for these rules, so it might not work 100% out of the box. (See more about this below)

Roadie also rewrites all relative URLs in the email to an absolute counterpart, making images you insert and those referenced in your stylesheets work. No more headaches about how to write the stylesheets while still having them work with emails from your acceptance environments.


  • Writes CSS styles inline.
    • Respects !important styles.
    • Does not overwrite styles already present in the style attribute of tags.
    • Supports the same CSS selectors as Nokogiri; use CSS3 selectors in your emails!
    • Keeps :hover and friends around in a separate <style> element.
  • Makes image urls absolute.
    • Hostname and port configurable on a per-environment basis.
  • Makes link hrefs and img srcs absolute.
  • Automatically adds proper HTML skeleton when missing; you don't have to create a layout for emails.
  • Allows you to inject stylesheets in a number of ways, at runtime.

Install & Usage

Add this gem to your Gemfile as recommended by Rubygems and run bundle install.

gem 'roadie', '~> 3.2'

You can then create a new instance of a Roadie document:

document = "<html><body></body></html>"
document.add_css "body { color: green; }"
    # => "<html><body style=\"color:green;\"></body></html>"

Your document instance can be configured with several options:

  • url_options - Dictates how absolute URLs should be built.
  • keep_uninlinable_css - Set to false to skip CSS that cannot be inlined.
  • asset_providers - A list of asset providers that are invoked when CSS files are referenced. See below.
  • external_asset_providers - A list of asset providers that are invoked when absolute CSS URLs are referenced. See below.
  • before_transformation - A callback run before transformation starts.
  • after_transformation - A callback run after transformation is completed.

Making URLs absolute

In order to make URLs absolute you need to first configure the URL options of the document.

html = '... <a href="/about-us">Read more!</a> ...'
document = html
document.url_options = {host: "", protocol: "https"}
  # => "... <a href=\"\">Read more!</a> ..."

The following URLs will be rewritten for you:

  • a[href] (HTML)
  • img[src] (HTML)
  • url() (CSS)

Referenced stylesheets

By default, style and link elements in the email document's head are processed along with the stylesheets and removed from the head.

You can set a special data-roadie-ignore attribute on style and link tags that you want to ignore (the attribute will be removed, however). This is the place to put things like :hover selectors that you want to have for email clients allowing them.

Style and link elements with media="print" are also ignored.

  <link rel="stylesheet" type="text/css" href="/assets/emails/rock.css">         <!-- Will be inlined with normal providers -->
  <link rel="stylesheet" type="text/css" href="">  <!-- Will be inlined with external providers, *IF* specified; otherwise ignored. -->
  <link rel="stylesheet" type="text/css" href="/assets/jazz.css" media="print">  <!-- Will NOT be inlined; print style -->
  <link rel="stylesheet" type="text/css" href="/ambient.css" data-roadie-ignore> <!-- Will NOT be inlined; ignored -->
  <style></style>                    <!-- Will be inlined -->
  <style data-roadie-ignore></style> <!-- Will NOT be inlined; ignored -->

Roadie will use the given asset providers to look for the actual CSS that is referenced. If you don't change the default, it will use the Roadie::FilesystemProvider which looks for stylesheets on the filesystem, relative to the current working directory.


# /home/user/foo/stylesheets/primary.css
body { color: green; }

# /home/user/foo/script.rb
html = "<html>\n<head>\n<link rel=\"stylesheet\" type=\"text/css\" href=\"/stylesheets/primary.css\">\n</head>\n<body>\n</body>\n</html>\n"

Dir.pwd # => "/home/user/foo"
document = html
document.transform # =>
                   # <!DOCTYPE html>
                   # <html>
                   #   <head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head>
                   #   <body style="color:green;"></body>
                   # </html>

If a referenced stylesheet cannot be found, the #transform method will raise an Roadie::CssNotFound error. If you instead want to ignore missing stylesheets, you can use the NullProvider.

Configuring providers

You can write your own providers if you need very specific behavior for your app, or you can use the built-in providers. Providers come in two groups: normal and external. Normal providers handle paths without host information (/style/foo.css) while external providers handle URLs with host information (//, localhost:3001/bar.css, and so on).

The default configuration is to not have any external providers configured, which will cause those referenced stylesheets to be ignored. Adding one or more providers for external assets causes all of them to be searched and inlined, so if you only want this to happen to specific stylesheets you need to add ignore markers to every other styleshheet (see above).

Included providers:

  • FilesystemProvider – Looks for files on the filesystem, relative to the given directory unless otherwise specified.
  • ProviderList – Wraps a list of other providers and searches them in order. The asset_providers setting is an instance of this. It behaves a lot like an array, so you can push, pop, shift and unshift to it.
  • NullProvider – Does not actually provide anything, it always finds empty stylesheets. Use this in tests or if you want to ignore stylesheets that cannot be found by your other providers (or if you want to force the other providers to never run).
  • NetHttpProvider – Downloads stylesheets using Net::HTTP. Can be given a whitelist of hosts to download from.
  • CachedProvider – Wraps another provider (or ProviderList) and caches responses inside the provided cache store.
  • PathRewriterProvider – Rewrites the passed path and then passes it on to another provider (or ProviderList).

If you want to search several locations on the filesystem, you can declare that:

document.asset_providers = ["resources", "stylesheets")),"system", "uploads", "stylesheets")),


If you want to ignore stylesheets that cannot be found instead of crashing, push the NullProvider to the end:

# Don't crash on missing assets
document.asset_providers <<

# Don't download assets in tests

Note: This will cause the referenced stylesheet to be removed from the source code, so email client will never see it either.


The NetHttpProvider will download the URLs that is is given using Ruby's standard Net::HTTP library.

You can give it a whitelist of hosts that downloads are allowed from:

document.external_asset_providers << ["", "", ""])
document.external_asset_providers << # Allows every host


You might want to cache providers from working several times. If you are sending several emails quickly from the same process, this might also save a lot of time on parsing the stylesheets if you use in-memory storage such as a hash.

You can wrap any other kind of providers with it, even a ProviderList:

document.external_asset_providers =, my_cache)

If you don't pass a cache backend, it will use a normal Hash. The cache store must follow this protocol:

my_cache["key"] = some_stylesheet_instance # => #<Roadie::Stylesheet instance>
my_cache["key"]                            # => #<Roadie::Stylesheet instance>
my_cache["missing"]                        # => nil

Warning: The default Hash store will never be cleared, so make sure you don't allow the number of unique asset paths to grow too large in a single run. This is especially important if you run Roadie in a daemon that accepts arbritary documents, and/or if you use hash digests in your filenames. Making a new instance of CachedProvider will use a new Hash instance.

You can implement your own custom cache store by implementing the [] and []= methods.

class MyRoadieMemcacheStore
  def initialize(memcache)
    @memcache = memcache

  def [](path)
    css ="assets/#{path}/css")
    if css
      name ="assets/#{path}/name") || "cached #{path}", css)

  def []=(path, stylesheet)
    memcache.write("assets/#{path}/css", stylesheet.to_s)
    stylesheet # You need to return the set Stylesheet

document.external_asset_providers =

If you are using Rspec, you can test your implementation by using the shared examples for the "roadie cache store" role:

require "roadie/rspec"

describe MyRoadieMemcacheStore do
  let(:memcache_client) { MemcacheClient.instance }
  subject { }

  it_behaves_like "roadie cache store" do
    before { memcache_client.clear }


With this provider, you can rewrite the paths that are searched in order to more easily support another provider. Examples could include rewriting absolute URLs into something that can be found on the filesystem, or to access internal hosts instead of external ones.

filesystem ="assets")
document.asset_providers << do |path|
  path.sub('stylesheets', 'css').downcase

document.external_asset_providers = do |url|
  if url =~ /myapp\.com/
    URI.parse(url).path.sub(%r{^/assets}, '')

You can also wrap a list, for example to implement external_asset_providers by composing the normal asset_providers:

document.external_asset_providers = do |url|

Writing your own provider

Writing your own provider is also easy. You need to provide:

  • #find_stylesheet(name), returning either a Roadie::Stylesheet or nil.
  • #find_stylesheet!(name), returning either a Roadie::Stylesheet or raising Roadie::CssNotFound.
class UserAssetsProvider
  def initialize(user_collection)
    @user_collection = user_collection

  def find_stylesheet(name)
    if name =~ %r{^/users/(\d+)\.css$}
      user = @user_collection.find_user($1)"user #{} stylesheet", user.stylesheet)

  def find_stylesheet!(name)
    find_stylesheet(name) or raise, "does not match a user stylesheet", self)

  # Instead of implementing #find_stylesheet!, you could also:
  #     include Roadie::AssetProvider
  # That will give you a default implementation without any error message. If
  # you have multiple error cases, it's recommended that you implement
  # #find_stylesheet! without #find_stylesheet and raise with an explanatory
  # error message.

# Try to look for a user stylesheet first, then fall back to normal filesystem lookup.
document.asset_providers = [,'./stylesheets'),

You can test for compliance by using the built-in RSpec examples:

require 'spec_helper'
require 'roadie/rspec'

describe MyOwnProvider do
  # Will use the default `subject` (
  it_behaves_like "roadie asset provider", valid_name: "found.css", invalid_name: "does_not_exist.css"

  # Extra setup just for these tests:
  it_behaves_like "roadie asset provider", valid_name: "found.css", invalid_name: "does_not_exist.css" do
    subject { }
    before { stub_dependencies }

Keeping CSS that is impossible to inline

Some CSS is impossible to inline properly. :hover and ::after comes to mind. Roadie tries its best to keep these around by injecting them inside a new <style> element in the <head>.

The problem here is that Roadie cannot possible adjust the specificity for you, so they will not apply the same way as they did before the styles were inlined.

Another caveat is that a lot of email clients does not support this (which is the entire point of inlining in the first place), so don't put anything important in here. Always handle the case of these selectors not being part of the email.

Specificity problems

Inlined styles will have much higher specificity than styles in a <style>. Here's an example:

<style>p:hover { color: blue; }</style>
<p style="color: green;">Hello world</p>

When hovering over this <p>, the color will not change as the color: green rule takes precedence. You can get it to work by adding !important to the :hover rule.

It would be foolish to try to automatically inject !important on every rule automatically, so this is a manual process.

Turning it off

If you'd rather skip this and have the styles not possible to inline disappear, you can turn off this feature by setting the keep_uninlinable_css option to false.

document.keep_uninlinable_css = false


Callbacks allow you to do custom work on documents before they are transformed. The Nokogiri document tree is passed to the callable along with the Roadie::Document instance:

class TrackNewsletterLinks
  def call(dom, document)
    dom.css("a").each { |link| fix_link(link) }

  def fix_link(link)
    divider = (link['href'] =~ /?/ ? '&' : '?')
    link['href'] = link['href'] + divider + 'source=newsletter'

document.before_transformation = proc { |dom, document| logger.debug "Inlining document with title #{dom.at_css('head > title').try(:text)}" }
document.after_transformation =


You can configure the underlying HTML/XML engine to output XHTML or HTML (which is the default). One usecase for this is that { tokens usually gets escaped to &#123;, which would be a problem if you then pass the resulting HTML on to some other templating engine that uses those tokens (like Handlebars or Mustache).

document.mode = :xhtml

Build Status

Tested with Travis CI using:

  • MRI 2.1
  • MRI 2.2
  • MRI 2.3
  • MRI 2.4
  • JRuby (latest)
  • Rubinius (failures on Rubinius will not fail the build due to a long history of instability in rbx)

(Build status)

Let me know if you want any other VM supported officially.


This project follows Semantic Versioning and has been since version 1.0.0.


Why is my markup changed in subtle ways?

Roadie uses Nokogiri to parse and regenerate the HTML of your email, which means that some unintentional changes might show up.

One example would be that Nokogiri might remove your &nbsp;s in some cases.

Another example is Nokogiri's lack of HTML5 support, so certain new element might have spaces removed. I recommend you don't use HTML5 in emails anyway because of bad email client support (that includes web mail!).

I'm getting segmentation faults (or other C-like problems)! What should I do?

Roadie uses Nokogiri to parse the HTML of your email, so any C-like problems like segfaults are likely in that end. The best way to fix this is to first upgrade libxml2 on your system and then reinstall Nokogiri. Instructions on how to do this on most platforms, see Nokogiri's official install guide.

What happened to my @keyframes?

The CSS Parser used in Roadie does not handle keyframes. I don't think any email clients do either, but if you want to keep on trying you can add them manually to a <style> element (or a separate referenced stylesheet) and tell Roadie not to touch them.


Running specs

bundle install


Roadie is set up with the assumption that all CSS and HTML passing through it is under your control. It is not recommended to run arbritary HTML with the default settings.

Care has been given to try to secure all file system accesses, but it is never guaranteed that someone cannot access something they should not be able to access.

In order to secure Roadie against file system access, only use your own asset providers that you yourself can secure against your particular environment.

If you have found any security vulnerability, please email me at to disclose it. For very sensitive issues, please use my public GPG key. You can also encrypt your message with my public key and open an issue if you do not want to email me directly. Thank you.

History and contributors

This gem was previously tied to Rails. It is now framework-agnostic and supports any type of HTML documents. If you want to use it with Rails, check out roadie-rails.

Major contributors to Roadie:

You can see all contributors on GitHub.


(The MIT License)

Copyright (c) 2009-2017 Magnus Bergmark, Jim Neath / Purify, and contributors.

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.