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
styleandlink[rel=stylesheet]tags and preserves existing inline attributes
- Checks
- Relative paths are converted to absolute paths
- Checks links in
href,srcand CSSurl('')
- Checks links in
- CSS properties are checked against e-mail client capabilities
- Based on the Email Standards Project's guides
- A plain text version is created (optional)
Installation
Install the Premailer gem from RubyGems.
gem install premaileror add it to your Gemfile and run bundle.
Example
require 'premailer'
premailer = Premailer.new('http://example.com/myfile.html', :warn_level => Premailer::Warnings::SAFE)
# Write the plain-text output
# This must come before to_inline_css (https://github.com/premailer/premailer/issues/201)
File.open("output.txt", "w") do |fout|
fout.puts premailer.to_plain_text
end
# Write the HTML output
File.open("output.html", "w") do |fout|
fout.puts premailer.to_inline_css
end
# Output any CSS warnings
premailer.warnings.each do |w|
puts "#{w[:message]} (#{w[:level]}) may not render properly in #{w[:clients]}"
endAdapters
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)
- nokogiri (default)
- nokogiri_fast
- 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_fastRuby Compatibility
See .github/workflows/actions.yml for which ruby versions are tested. JRuby support is close, contributors are welcome.
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 = Premailer.new(html_string, with_html_string: true, drop_unmergeable_css_rules: true)See here for a full list of the available options.
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 source code can be found on GitHub.
Copyright by Alex Dunae (dunae.ca, e-mail 'code' at the same domain), 2007-2017. See LICENSE.md for license details.
