There's a lot of open issues
A long-lived project that still receives updates
Improve the rendering of HTML emails by making CSS inline, converting links and warning about unsupported code.
 Project Readme

Premailer README Build Status Gem Version

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)


Install the Premailer gem from RubyGems.

gem install premailer

or add it to your Gemfile and run bundle.


require 'premailer'

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

# Write the plain-text output
# This must come before to_inline_css ("output.txt", "w") do |fout|
  fout.puts premailer.to_plain_text

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

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


Premailer's default adapter is nokogiri if both nokogiri and nokogumbo are included in the Gemfile list. However, if you want to use a different adapter, you can choose to.

There are three adapters in total (as of premailer 1.10.0)

  1. nokogiri (default)
  2. nokogiri_fast
  3. nokogumbo

hpricot adapter removed due to its EOL, please use ~>1.9.0 version if You still need it..

NokogiriFast adapter improves the Algorithmic complexity of the running time by 20x with a slight compensation on memory. To switch to any of these adapters, add the following line. For example, if you want to include the NokogiriFast adapter,

Premailer::Adapter.use = :nokogiri_fast

Ruby Compatibility

See .travis.yml for which ruby versions are tested. 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
-premailer-align Available on table elements
data-premailer="ignore" Available on link and 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'>

Configuration options

The behavior of Premailer can be configured by passing options in the initializer.

For example, the following will accept HTML from a string and will exclude unmergeable css from being added to the <head> of the output document.

premailer =, with_html_string: true, drop_unmergeable_css_rules: true)

See here for a full list of the available options.


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 source code can be found on GitHub.

Copyright by Alex Dunae (, e-mail 'code' at the same domain), 2007-2017. See for license details.