premailer-rails

CSS styled emails without the hassle.

Introduction

This gem is a drop in solution for styling HTML emails with CSS without having to do the hard work yourself.

Styling emails is not just a matter of linking to a stylesheet. Most clients, especially web clients, ignore linked stylesheets or <style> tags in the HTML. The workaround is to write all the CSS rules in the style attribute of each tag inside your email. This is a rather tedious and hard to maintain approach.

Premailer to the rescue! The great premailer gem applies all CSS rules to each matching HTML element by adding them to the style attribute. This allows you to keep HTML and CSS in separate files, just as you're used to from web development, thus keeping your sanity.

This gem is an adapter for premailer to work with actionmailer out of the box. Actionmailer is the email framework used in Rails, which also works outside of Rails. Although premailer-rails has certain Rails specific features, it also works in the absence of Rails making it compatible with other frameworks such as sinatra.

premailer-rails works with actionmailer by registering a delivery hook. This causes all emails that are delivered to be processed by premailer-rails. This means that, by simply including premailer-rails in your Gemfile, you'll get styled emails without having to set anything up.

Installation

Simply add the gem to your Gemfile:

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. Since hpricot is no longer maintained, I suggest you to go with nokogiri. Add either one to your Gemfile:

gem 'nokogiri'
# or
gem 'hpricot'

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

That's it!

Configuration

Premailer itself accepts a number of options. In order for premailer-rails to pass these options on to the underlying premailer instance, specify them as follows (in Rails you could do that in an initializer such as config/initializers/premailer_rails.rb):

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',
  generate_text_part: true
}

If you don't want to automatically 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 internally by premailer-rails and thus will be overridden.

Usage

premailer-rails processes all outgoing emails by default. If you wish to skip premailer for a certain email, simply set the :skip_premailer header:

class UserMailer < ActionMailer::Base
  def welcome_email(user)
    mail to: user.email,
         subject: 'Welcome to My Awesome Site',
         skip_premailer: true
  end
end