Premailer README

What is this?

For the best HTML e-mail delivery results, CSS should be inline. This is a huge pain and a simple newsletter becomes un-managable very quickly. This script is my solution.

CSS styles are converted to inline style attributes
- Checks style and link[rel=stylesheet] tags and preserves existing inline attributes
Relative paths are converted to absolute paths
- Checks links in href, src and CSS url('')
CSS properties are checked against e-mail client capabilities
- Based on the Email Standards Project's guides
A plain text version is created (optional)

Premailer 2.0 is coming

I'm looking for input on a version 2.0 update to Premailer. Please visit the Premailer 2.0 Planning Page and give me your feedback.

Installation

Install the Premailer gem from RubyGems.

gem install premailer

or add it to your Gemfile and run bundle.

Example

require 'rubygems' # optional for Ruby 1.9 or above.
require 'premailer'

premailer = Premailer.new('http://example.com/myfile.html', :warn_level => Premailer::Warnings::SAFE)

# Write the HTML output
File.open("output.html", "w") do |fout|
  fout.puts premailer.to_inline_css
end

# Write the plain-text output
File.open("output.txt", "w") do |fout|
  fout.puts premailer.to_plain_text
end

# Output any CSS warnings
premailer.warnings.each do |w|
  puts "#{w[:message]} (#{w[:level]}) may not render properly in #{w[:clients]}"
end

Ruby Compatibility

Premailer is tested on Ruby 1.8.7, Ruby 1.9.2, Ruby 1.9.3, and Ruby 2.0.0 . It also works on REE. JRuby support is close; contributors are welcome. Checkout the latest build status on the Travis CI dashboard.

Premailer-specific CSS

Premailer looks for a few CSS attributes that make working with tables a bit easier.

CSS Attribute	Availability
-premailer-width	Available on `table`, `th` and `td` elements
-premailer-height	Available on `table`, `tr`, `th` and `td` elements
-premailer-cellpadding	Available on `table` elements
-premailer-cellspacing	Available on `table` elements
data-premailer="ignore"	Available on `style` elements. Premailer will ignore these elements entirely.

Each of these CSS declarations will be copied to appropriate element's attribute.

For example

table { -premailer-cellspacing: 5; -premailer-width: 500; }

will result in

<table cellspacing='5' width='500'>

Contributions

Contributions are most welcome. Premailer was rotting away in a private SVN repository for too long and could use some TLC. Fork and patch to your heart's content. Please don't increment the version numbers, though.

A few areas that are particularly in need of love:

Improved test coverage
Move un-repeated background images defined in CSS for Outlook

Credits and code

Thanks to all the wonderful contributors for their updates.

Thanks to Greenhood + Company for sponsoring some of the 1.5.6 updates, and to Campaign Monitor for supporting the web interface.

The web interface can be found at premailer.dialect.ca.

The source code can be found on GitHub.

constantcontact/premailer