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.


Download the Premailer gem from RubyGems.

gem install premailer


premailer ='', :warn_level => Premailer::Warnings::SAFE)

# Write the HTML output
fout ="output.html", "w")
fout.puts premailer.to_inline_css

# Write the plain-text output
fout ="ouput.txt", "w")
fout.puts premailer.to_plain_text

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

Ruby Compatibility

Premailer is tested on Ruby 1.8.7, Ruby 1.9.2 and Ruby 1.9.3 (preview 1). 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.

Available on table, th and td elements
Available on table, tr, th and td elements
Available on table elements
Available on table elements

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 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

The source code can be found on GitHub.

Copyright by Alex Dunae (, e-mail 'code' at the same domain), 2007-2012. See for license details.