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Markdown + oEmbed + Sanitize + CodeRay = the ultimate user input rendering pipeline!
branch: master


slodown is the ultimate user input rendering pipeline.

Build Status Gem Version

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!
  • add syntax highlighting to Markdown code blocks through CodeRay.
  • support 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 some or all transformations on it. Finally, call #to_s to get the rendered output.


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

# just extract metadata

# 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:


Slodown allows metadata, such as the creation date, to be defined in the text to be processed:

#+title: Slodown
#+created_at: 2014-03-01 13:51:12 CET
# Installation

Add this line to your application's Gemfile:

    gem 'slodown'


Metadata can be accessed with Slodown::Formatter#metadata:

formatter.metadata[:title] # => "Slodown"


  • 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.


Just like with my other gems, I am trying to keep slodown as sane (and small) as possible. If you want to contribute code, please talk to me before writing a patch or submitting a pull request! I'm serious about keeping things focused and would hate to cause unnecessary disappointment. Thank you.

If you're still set on submitting a pull request, please consider the following:

  1. Create your pull request from a feature branch.
  2. The pull request must only contain changes related to the feature.
  3. Please include specs where it makes sense.
  4. Absolutely no version bumps or similar.

Version History


  • Support for Twitter oEmbed (using an unfortunately deprecated API, nonetheless.)
  • Added Slodown::Formatter#kramdown_options, returning a hash of kramdown configuration options. Overload this in order to customize the formatter's behavior.


  • first public release
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