Markdown in Rails 3 with RedCarpet


updated Jan 2014 for Rails 4, see bottom

I just got this blog up and running yesterday, a marathon of pain but ultimately successful. So today I wanted to add some Markdown action so I didn't have to drop into TextMate to add <p> tags to everything all the time.

RedCarpet seemed to be the gem that was recommended, but it's recently seen a complete API overhaul that has rendered useless the vast majority of the de facto documentation out there. So, viewers of the Markdown Railscast, this one's for you.

It only involves a few changes, so if you're here it's likely that you know how to install it and you're here because of that "no 'new' method" error. Instead of

<%= %>

as mentioned in the Railscast, you'll need to do a little more setting up. This is how I did it.

# app/helpers/application_helper.rb

def dat_markdown(text)
  markdown =,
      :autolink => true, :space_after_headers => true, :no_intra_emphasis => true)

The first parameter is which renderer you want to use (either HTML or XHTML, for what?), and everything after that is your options glob which you can get from here. For readability you could also do -

# app/helpers/application_helper.rb

def dat_markdown(text)
  options = {
    :autolink => true,
    :space_after_headers => true,
    :no_intra_emphasis => true
  markdown =, options)

After that all you have to do is

<%= dat_markdown(@post.body) %>

and you're on your merry way. Enjoy.

January 2014 update

Rails 4 - check out Kramdown. This is how easy it is now.

# application_helper.rb

  def markdown_filter(text)

and <%= markdown_filter @post.body %>

Super bonus for the demographic reading this - syntax highlighting is included for free. See above. Docs for the options hash are here.