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This gem is a no config solution for the wonderful Premailer gem to be used with Rails. It uses interceptors which were introduced in Rails 3 and tweaks all mails which are delivered and adds a plain text part to them and inlines all CSS rules into the HTML part.

By default it inlines all the CSS files that are linked to in the HTML:

<link type='text/css' ... />

Don't worry about the host in the CSS URL since this will be ignored.

Every CSS file is loaded from within the app. The retrieval of the file depends on your assets configuration:

  • Rails 3.1 asset pipeline: It will load the compiled version of the CSS asset which is normally located in app/assets/stylesheets/. If the asset can't be found (e.g. it is only available on a CDN and not locally), it will be HTTP requested.

  • Classic static assets: It will try to load the CSS file located in public/stylesheets/

  • Hassle: It will try to load the compiled CSS file located in the default Hassle location tmp/hassle/stylesheets/


Simply add the gem to your Gemfile in your Rails project:

gem 'premailer-rails'

premailer-rails requires either nokogiri or hpricot. It doesn't list them as a dependency so you can choose which one to use.

gem 'nokogiri'
# or
gem 'hpricot'

If both are loaded for some reason, premailer chooses hpricot.

That's it!


Premailer itself accepts a number of options. In order for premailer-rails to pass these options on to the underlying premailer instance, specify them in an initializer:

Premailer::Rails.config.merge!(:preserve_styles => true,
                               :remove_ids      => true)

For a list of options, refer to the Premailer documentation

The default configs are:

  :input_encoding     => 'UTF-8',
  :inputencoding      => 'UTF-8',
  :generate_text_part => true

The input encoding option changed at some point. To make sure this option works regardless of the premailer version, the old and new setting is specified. If you want to use another encoding make sure to specify the right one or both.

If you don't want to generate a text part from the html part, set the config :generate_text_part to false.

Note that the options :with_html_string and :css_string are used to make this gem work and will thus be overridden.