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Markdown + oEmbed + Sanitize + CodeRay = the ultimate user input rendering pipeline!
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slodown is the ultimate user input rendering pipeline.

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I love Markdown. I love syntax highlighting. I love oEmbed. And last but not least, I love whitelist-based HTML sanitizing. slodown rolls all of these into one, and then some.

Here's what slodown does by default:

  • render extended Markdown into HTML. It uses the kramdown library, so yes, footnotes are supported!
  • adds syntax highlighting to Markdown code blocks through CodeRay.
  • supports super-easy rich media embeds, Just point the Markdown image syntax at, say, a Youtube video, and slodown will fetch the complete embed code through the magic of ruby-oembed.
  • auto-link contained URLs using Rinku, which is smart enough to not auto-link URLs contained in, say, code blocks.
  • sanitize the generated HTML using the white-list based sanitize gem.

slodown is an extraction from It is very easy to extend or modify, as it's just a plain old Ruby class you can inherit from.


Add this line to your application's Gemfile:

gem 'slodown'

And then execute:

$ bundle

Or install it yourself as:

$ gem install slodown


For every piece of user input that needs to be rendered, create an instance of Slodown::Formatter with the source text and use it to perform somre or all transformations on it. Finally, call #to_s to get the rendered output.


# let's create an instance to work with
formatter =

# just render Markdown to HTML

# just auto-link contained URLs

# just sanitize HTML tags

# you can chain multiple operations

# this is the whole deal:

# which is the same as:


  • If you want to add more transformations or change the behavior of the #complete method, just subclass Slodown::Formatter and go wild. :-)
  • Markdown transformations, HTML sanitizing, oEmbed handshakes and other operations are pretty expensive operations. For sake of performance (and stability), it is recommended that you cache the generated output in some manner.
  • Eat more Schnitzel.


  • More/better specs. slodown doesn't have a lot of functionality of its own, passing most of its duties over to the beautiful rendering gems it uses, but I'm sure there's still an opportunity or two for it to break, so, yeah, I should be adding some specs.
  • Better configuration for the HTML sanitizer. Right now, in order to change the sanitizing behavior, you'll need to inherit a new class from Slodown::Formatter and override its #sanitize_config method. Regarding the contents of the hash this method returns, please refer to the sanitize documentation.


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request
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