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Hologram is a Ruby gem that parses comments in your CSS and helps you turn them into a beautiful style guide.

There are two steps to building a great style guide:

  1. Documenting your css and javascript, and generating html examples.
  2. Styling the output of step 1.

The hologram gem itself is only concerned with step 1. This means you are free to make your style guide look however you would like. If you don't feel like going through this process yourself, you can take a look at the templates in our example repository, and use the assets defined there instead.


Add this line to your application's Gemfile:

gem 'hologram'

And then execute:

$ bundle

If you don't use bundler you can run gem install hologram.

Quick Start

hologram init

This will create a hologram_config.yml file (more on this below), starter _header.html and _footer.html files, and starter templates for rendering code examples. You can then tweak the config values and start documenting your css.

Add some documentation to one of your stylesheets:

title: Alert
name: alert
category: basics
    <div class='alert'>Hello</div>

Building the documentation is simply:


Command line flags

Hologram has a couple of command line flags:

  • -c or --config - specify the config file, by default hologram looks for hologram_config.yml


There are two things you need to do to start using hologram:

  1. Create a YAML config file for your project.

  2. Go document some code!

Creating a YAML config file

Hologram needs a few configuration settings before it can begin to build your documentation for you. Once this is set up, you can execute hologram by simply running:

hologram path/to/your/config.yml or (using bundler) bundle exec hologram path/to/your/config.yml

Your config file needs to contain the following key/value pairs

  • source: relative path(s) to your source files. Accepts either a single value or an array

  • destination: relative path where you want the documentation to be built

  • documentation_assets: The path that contains supporting assets for the documentation page. This typically includes html fragments (header/footer, etc), style guide specific CSS, javascript and any images. Hologram specifically looks for two files: _header.html and _footer.html. These are used to start and end every html page hologram generates.

    Hologram treats _header.html and _footer.html as ERB files for each page that is generated. You can access the title, file_name, blocks, and categories.

    blocks is a list of each documentation block on the page. Each item in the list has a title, name, category, and optionally a parent. This is useful for, say, building a menu that lists each component.

    categories is a list of all the categories found in the documentation

    Nota Bene: Filenames that begin with underscores will not be copied into the destination folder.

  • code_example_templates: (optional) Hologram uses the files in this folder to format the code examples in the styleguide. The initializer generates 4 files:

    • markup_example_template.html.erb - used for html, haml and slim examples

    • markup_table_template.html.erb - used for multiple html, haml and slim examples layed out in a table (see the tabular layout docs for more information)

    • js_example_template.html.erb - used for js examples

    • jsx_example_template.html.erb - used for jsx examples

    The html in the files will be rendered for every code example in the styleguide. The variable rendered_example represents the html generated by the example, while the variable code_example represents the formatted and escaped code behind the example.

    See the documentation on custom code renderers for more information,

    Nota Bene: If template files are missing, or this folder does not exist, hologram will use default templates.

  • code_example_renderers: (optional) A folder that contains your custom code renderers. For example, if you want to have coffee_examples in your code, write a coffeescript renderer and place it in this folder. See #custom_code_example_renders for more inforamtion on this.

  • custom_markdown: (optional) this is the filename of a class that extends RedCarpet::Render::HTML class. Use this for when you need additional classes or html tags for different parts of the page. See [example_markdown_renderer.rb.example] (example_markdown_renderer.rb.example) for an example of what your class can look like.

  • index: (optional) this is a category (see Documenting your styles section below) that will be used as the index.html.

  • dependencies: a list of relative paths to folders containing any dependencies your style guide has. These folders will be copied over into the documentation output directory. ENSURE THE CSS/JS THAT IS ACTUALLY BEING DOCUMENTED IS LISTED HERE. You will also need to ensure that they are included on your pages. A simple way to do this is to add <link> and <script src=> tags to the _header.html file.

  • ignore_paths: (optional) a list of paths to ignore. This can be a file name or a glob. Be sure to wrap globs in double quotes to keep yaml from getting too upset (ie good:".erb" vs bad:.erb).

  • nav_level: (optional) Sets the level of section navigation desired. section sets it to show sub navigation in top level sections. all sets it to show sub navigation for all sections. all can be a bit much, you'll probably want section.

  • custom_extensions: (optional) Additional file extensions that will be included in the parse. Accepts both a single value and an array. The current supported file extensions are .css, .scss, .less, .sass, .styl, .js, .md, .markdown and .erb.

  • exit_on_warnings: (optional) Hologram displays warnings when there are issues with your docs (e.g. if a component's parent is not found, if the _header.html and/or _footer.html files aren't found) If you want Hologram to exit on these warnings, set the value to 'true' (Default value is 'false')

Example config file
# Hologram will run from same directory where this config file resides
# All paths should be relative to there

# The directory containing the source files to parse recursively
source: ./sass

# You may alternately specify multiple directories.
# source:
#  - ./sass
#  - ./library-sass

# The directory that hologram will build to
destination: ./docs

# The assets needed to build the docs (includes header.html,
# footer.html, etc)
# You may put doc related assets here too: images, css, etc.
documentation_assets: ./doc_assets

# The folder that contains templates for rendering code examples.
# If you want to change the way code examples appear in the styleguide,
# modify the files in this folder
code_example_templates: ./code_example_templates

# The folder that contains custom code example renderers.
# If you want to create additional renderers that are not provided
# by Hologram (i.e. coffeescript renderer, jade renderer, etc)
# place them in this folder
code_example_renderers: ./code_example_renderers

# Any other asset folders that need to be copied to the destination
# folder. Typically this will include the css that you are trying to
# document. May also include additional folders as needed.
  - ./build

# Mark which category should be the index page
# Alternatively, you may have an in the source directory root
# folder instead of specifying this config.
index: basics

# To output navigation for top level sections, set the value to
# 'section'. To output navigation for sub-sections, set the value to `all`
nav_level: all

# Hologram displays warnings when there are issues with your docs
# (e.g. if a component's parent is not found, if the _header.html and/or
#  _footer.html files aren't found)
# If you want Hologram to exit on these warnings, set the value to 'true'
# (Default value is 'false')
exit_on_warnings: false

Documenting your styles and components

Hologram will scan for stylesheets (.css, .scss, .sass, .less, or .styl) and javascript source files (.js) within the source directory defined in your configuration. It will look for comments that match the following:

title: Buttons
name: button
category: Base CSS

Button styles can be applied to any element. Typically you'll want
to use either a `<button>` or an `<a>` element:

```html_example <button class="btn btnDefault">Click</button> <a
class="btn btnDefault" href="">Trulia!</a> ```

If your button is actually a link to another page, please use the
`<a>` element, while if your button performs an action, such as
submitting a form or triggering some javascript event, then use a
`<button>` element.


NB: Sass users who are using the .sass flavor of Sass should use //doc style comments with indents to create their comment blocks.

The first section of the comment is a YAML block that defines certain aspects of this documentation block (more on that in the next section). The second part is simply markdown as defined by Redcarpet.

Notice the use of html_example. This tells the markdown renderer that it should treat the example as...well...html. If your project uses haml you can also use haml_example. In that case the output will be html for the example and the code block will show the haml used to generate the html.

For components that require javascript you can use js_example. In addition to outputting the javascript in a <code> block it will also wrap it in a <script> tag for execution.

Additionally, html elements that are generated via markdown will have a class styleguide appended to them. You can use this to apply css to the styleguide itself.

Tabular layout for component documentation

If you want the code snippet next to the rendered component, instead of below, render your component horizontally by applying the html_example_table or haml_example_table modifiers to the code block.

title: Buttons
name: button
category: Base CSS

<button class="btn btnDefault">Click</button>

<a class="btn btnDefault" href="">Trulia!</a>


NB: Components separated by a blank line will be rendered as separate table rows.

Referencing other components

For some components, you may want to reference the documentation of another component. As an example, you may want your link components to link to the button documentation.

title: Links
name: links
category: Other Category


You may want to use a button for a link.
See [the button documentation][button] for more info.


You can use a reference link of the form [link description][component_name] to link to any other component in the styleguide. These links will even work if the referenced component belongs to a different category.

Document YAML section

The YAML in the documentation block can have any key/value pairs you deem important, but it specifically looks for the following keys:

  • title: The title to display in the documents
  • category/categories: This is the broad categories for the component, all components in the same category will be written to the same page. It can be set to either a string or a YAML array. If you use an array, the component will be written to both pages. Note: There is no need to set a category if this component has a parent.
  • name: This is used for grouping components, by assigning a name, a component can be referenced in another component as a parent. Note that items in the same category are sorted alphabetically by name.
  • parent: (Optional.) This should be the name of another component. If this is set, the current component will be displayed as a section within the parent's documentation, but only if it specifies the same category, or allows the category to be inherited from its parent.
  • hologram: (markdown only) To avoid conflicts with Jekyll and other YAML+markdown formats, Markdown (.md) files must include a hologram: true key/value pair in the YAML block to indicate that it is intended to be processed by Hologram.

For example, you might have a component with the name buttons and another component named buttonSkins. You could set the parent for the buttonSkins component to be buttons. It would then nest the buttonSkins documentation inside the buttons documentation.

Each level of nesting (components are infinitely nestable) will have a heading tag that represents its depth. In the above example buttons would have an <h1> and buttonSkins would have an <h2>.

You can see this exact example in our demo repo, and the output of this nesting in our demo style guide.

Documentation Assets

The documentation assets folder contains the html, css, js and images you'll need for making your style guide look beautiful.

Hologram doesn't care too much about what is in here as it is intended to be custom for your style guide.

Styling Your Code Examples

Hologram uses pygments.rb gem to provide syntax highlighting for code examples. One of the assets that you probably want to include in your documentation assets folder is a css file that styles the "pygmentized" code examples. We use github.css which can be found along with the css we use to style code blocks here.

Custom Code Example Renderers

By default, hologram supports the following code example types:

  • html_example and html_example_table
  • haml_example and haml_example_table
  • slim_example and slim_example_table
  • js_example
  • jsx_example

Let's say you want to include coffeescript examples in your styleguide. You'll need to create a custom renderer for this.

First, if none of the included templates (markup_example_template, js_example_template, etc) work for you, create new custom template files. In this example, let's say you have the templates my_custom_coffee_example_template.html.erb and my_custom_coffee_table_template.html.erb in your ./code_example_templates folder.

<!-- ./code_example_templates/my_custom_coffee_example_template.html.erb -->

<script><%= rendered_example %></script>
<div class="codeBlock coffeeExample">
  <div class="highlight">
    <pre><%= code_example %></pre>
<!-- ./code_example_templates/my_custom_coffee_table_template.html.erb -->

<div class="codeTable">
      <% examples.each do |example| %>
            <script><%= example.rendered_example %></script>
            <div class="codeBlock coffeeExample">
              <div class="highlight">
                <pre><%= example.code_example %></pre>
      <% end %>

Next, create a custom renderer for coffeescript in the file ./code_example_renderers/coffee_renderer.rb.

# ./code_example_renderers/coffee_renderer.rb

require 'coffee-script'

Hologram::CodeExampleRenderer::Factory.define('coffee') do
  example_template 'my_custom_coffee_example_template'
  table_template 'my_custom_coffee_table_template'

  lexer { Rouge::Lexer.find(:coffee) }

  rendered_example do |code|

Now you should be able to render coffeescript examples in your styleguide. You can render single coffeescript examples...

$('#myDiv').click ->
  alert 'Oh wow we are rendering coffee script'

Or you can render coffeescript tables...

$('#myDiv').click ->
  alert 'Oh wow we are rendering coffee script'

$('#myOtherDiv').click ->
  console.log 'Yeah coffee script!'

$('#yetAnotherDiv').click ->
  window.location =

Here's some details on the code example renderer factory:

  • Hologram::CodeExampleRenderer::Factory.define(example_type, &block) - this is how you declare a custom renderer. example_type is the name of the renderer, and determines the example name. For example, if example_type was "foobar", in your styleguide you can create foobar_examples and foobar_example_tables

  • example_template - the name of the template used to render the example, minus the .html.erb extension (e.g. "markup_example_template"). It should live in your code_example_templates folder

  • table_template - (optional) the name of the template used to render examples in tabular form, minus the extension (e.g. "markup_table_template").

  • lexer - (optional) a Rogue Lexer that matches the syntax of your example (i.e. Rouge::Lexer.find(:haml), Rouge::Lexer.find(:ruby)). Here's a complete list of possible lexers. If this argument is not provided, hologram will guess what the best one is.

  • rendered_example - (optional) this is the set of instructions to "translate" your exaple so it can be rendered. I.e. for coffeescript to be "rendered" in the browser, you need to transform it to javascript (as can be seen in the block above). For haml, you need to transform it to html. If no block is provided, the code is rendered as is.

Supported Preprocessors/File Types

The following preprocessors/file types are supported by Hologram:

  • Sass (.scss, .sass)
  • Less (.less)
  • Stylus (.styl)
  • Vanilla CSS (.css)
  • Javascript (.js)
  • Markdown (.md, .markdown)

Extensions and Plugins

  • Guard Hologram is a sweet little gem that uses guard to monitor changes to your hologram project and rebuilds your style guide on the fly as you make changes.
  • Grunt Hologram is a sweet little grunt task that will generate your hologram style guide.
  • Hologram Plugin for Gulp is a gulp task for hologram.
  • Classname Clicker is a handy UI addition that gives the ability to see rules that apply to a classname by clicking on them within hologram.
  • Cortana is a theme for hologram. It also includes a handy search feature.
  • Hologram Github Theme is a Github Styleguide inspired theme for hologram.
  • Voxel Hologram is a minimal theme for Hologram.
  • Acme Styleguide is a starter project that helps Pivotal Labs Designers build living styleguides with Sass and Hologram.


  1. Fork it
  2. Create your feature/bug fix 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


Hologram is written and maintained by August Flanagan and JD Cantrell.


These fine people have also contributed to making hologram a better gem:


Hologram is licensed under the MIT License