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Rouge is a pure-ruby syntax highlighter. It can highlight 100 different languages, and output HTML or ANSI 256-color text. Its HTML output is compatible with stylesheets designed for pygments.

If you'd like to help out with this project, assign yourself something from the issues page, and send me a pull request (even if it's not done yet!). Bonus points for feature branches.


First, take a look at the pretty colors.

# make some nice lexed html
source ='/etc/bashrc')
formatter =
lexer =

# Get some CSS
Rouge::Themes::Base16.mode(:light).render(scope: '.highlight')
# Or use Theme#find with string input
Rouge::Theme.find('base16.light').render(scope: '.highlight')

Full options


As of Rouge 2.0, you are encouraged to write your own formatter for custom formatting needs. Builtin formatters include:

  • - will render your code with standard class names for tokens, with no div-wrapping or other bells or whistles.
  • - will render your code with no class names, but instead inline the styling options into the style= attribute. This is good for emails and other systems where CSS support is minimal.
  •, class: 'line-%i') This formatter will split your code into lines, each contained in its own div. The class option will be used to add a class name to the div, given the line number.
  •, css_class='codehilite') wraps the given formatter with div wrappers generally expected by stylesheets designed for Pygments.
  •, opts={}) will output an HTML table containing numbered lines. Options are:
    • start_line: 1 - the number of the first line
    • line_format: '%i' - a sprintf template for the line number itself
    • table_class: 'rouge-table' - a CSS class for the table
    • gutter_class: 'rouge-gutter' - a CSS class for the gutter
    • code_class: 'rouge-code' - a CSS class for the code column
  •{}) is a backwards-compatibility class intended for users of rouge 1.x, with options that were supported then. Options are:
    • inline_theme: nil - use an HTMLInline formatter with the given theme
    • line_numbers: false - use an HTMLTable formatter
    • wrap: true - use an HTMLPygments wrapper
    • css_class: 'codehilite' - a CSS class to use for the pygments wrapper
    • theme must be an instnce of Rouge::Theme, or a Hash structure with :theme entry

Lexer options

debug: false

Print a trace of the lex on stdout

parent: ''

Allows you to specify which language the template is inside

CSS theme options

scope: '.highlight'

CSS selector that styles are applied to, e.g. Rouge::Themes::MonokaiSublime.render(scope: 'code')

Rouge aims to be simple to extend, and to be a drop-in replacement for pygments, with the same quality of output. Also, Rouge ships with a rougify command which allows you to easily highlight files in your terminal:

$ rougify foo.rb
$ rougify style monokai.sublime > syntax.css

Advantages to pygments.rb

Advantages to CodeRay

  • The HTML output from Rouge is fully compatible with stylesheets designed for pygments.
  • The lexers are implemented with a dedicated DSL, rather than being hand-coded.
  • Rouge supports every language CodeRay does and more.

You can even use it with Redcarpet

require 'redcarpet'
require 'rouge'
require 'rouge/plugins/redcarpet'

class HTML < Redcarpet::Render::HTML
  include Rouge::Plugins::Redcarpet # yep, that's it.

If you have :fenced_code_blocks enabled, you can specify languages, and even options with CGI syntax, like php?start_inline=1, or erb?parent=javascript.


Rouge is only for UTF-8 strings. If you'd like to highlight a string with a different encoding, please convert it to UTF-8 first.

Other integrations


Installing Ruby

If you're here to implement a lexer for your awesome language, there's a good chance you don't already have a ruby development environment set up. Follow the instructions on the wiki to get up and running. If you have trouble getting set up, let me know - I'm always happy to help.

Run the tests

You can test the core of Rouge simply by running rake (no bundle exec required), or rake spec TEST=spec/xxx_spec.rb to run a single test file.

It's also set up with guard, if you like.

To test a lexer visually, run rackup from the root and go to localhost:9292/#{some_lexer} where some_lexer is the tag or an alias of a lexer you'd like to test. If you add ?debug=1, helpful debugging info will be printed on stdout.

API Documentation

is at

Using the lexer DSL

You can probably learn a lot just by reading through the existing lexers. Basically, a lexer consists of a collection of states, each of which has several rules. A rule consists of a regular expression and an action, which yields tokens and manipulates the state stack. Each rule in the state on top of the stack is tried in order until a match is found, at which point the action is run, the match consumed from the stream, and the process repeated with the new lexer on the top of the stack. Each lexer has a special state called :root, and the initial state stack consists of just this state.

Here's how you might use it:

class MyLexer < Rouge::RegexLexer
  state :root do
    # the "easy way"

    # simple rules
    rule /0x[0-9a-f]+/, Num::Hex

    # simple state stack manipulation
    rule /{-/, Comment, :next_state
    rule /-}/, Comment, :pop!

    # the "flexible way"
    rule /abc/ do |m|
      # m is the match, for accessing match groups manually

      # you can do the following things:
      push :another_state
      push # assumed to be the current state
      state? :some_state # check if the current state is :some_state
      in_state? :some_state # check if :some_state is in the state stack

      # yield a token.  if no second argument is supplied, the value is
      # taken to be the whole match.
      # The sum of all the tokens yielded must be equivalent to the whole
      # match - otherwise characters will go missing from the user's input.
      token Generic::Output, m[0]

      # calls SomeOtherLexer.lex(str) and yields its output.  See the
      # HTML lexer for a nice example of this.
      # if no second argument is supplied, it is assumed to be the whole
      # match string.
      delegate SomeOtherLexer, str

      # the context object is the lexer itself, so you can stash state here
      @count ||= 0
      @count += 1

      # advanced: push a dynamically created anonymous state
      push do
        rule /.../, Generic::Output

    rule /(\w+)(:)/ do
      # "groups" yields the matched groups in order
      groups Name::Label, Punctuation

  start do
    # this is run whenever a fresh lex is started

If you're creating a lexer that's very similar to a different lexer, you can use subclassing (see C/C++/ObjC and also QML/Javascript for examples):

class MyLexer < OtherLexer
  # independent states
  state :my_state do ... end

  # override states
  state :your_state do ... end

  # prepend rules to states
  prepend :parent_state do ... end

  # append rules to states
  append :parent_state do ... end

Please don't submit lexers that are largely copy-pasted from other files.


I don't get paid to maintain rouge. If you've found this software useful, consider dropping a tip in the bucket.


Rouge is released under the MIT license. Please see the LICENSE file for more information.