Markaby (Markup as Ruby)

Markaby is a very short bit of code for writing HTML pages in pure Ruby. It is an alternative to ERb which weaves the two languages together. Also a replacement for templating languages which use primitive languages that blend with HTML.

Install it

Just do what everyone else does:

# in Gemfile:
gem 'markaby'

then bundle install:

bundle install

Using Markaby with Rails 4/5+:

Install the gem (using bundler), then:

# in config/initializers/markaby.rb:

require 'markaby/rails'

  tagset: Markaby::HTML5,
  indent: 2,

Name your templates with an html.mab extension. You’ll also want to configure your text editor to see .mab as ruby.

Here’s how you’d do that for Atom:

  1. Install the file-types module:

    apm install file-types
  2. in your config: Atom -> Config:

        "\\.mab$": "source.ruby"

Now that’s some chunky bacon!

Using Markaby in helpers:

Just call Markaby::Builder with a block as below.

You can also require ‘markaby/kernel_method’ to make it even easier:

# my_helper.rb:
require 'markaby/kernel_method' # or put this in an initializer

module MyHelper
  # note - you can also use { }.to_s
  def chunky_bacon
    mab do
      p "Chunky Bacon!"

Using Markaby with Sinatra (1.0+)

get '/foo' do
  mab :my_template # my_template.mab in the sinatra view path

If you are looking for sinatra support pre 0.7, see

Using Markaby with other frameworks

Tilt has a Markaby module, so in principle, any web framework that supports Tilt will also support Markaby. See the appropriate tilt documentation:

Using Markaby as a Ruby class

Markaby is flaming easy to call from your Ruby classes.

require 'markaby'

mab =
mab.html do
  head { title "" }
  body do
    h1 " has great deals"
    ul do
      li "$49 for a canoe"
      li "$39 for a raft"
      li "$29 for a huge boot that floats and can fit 5 people"
puts mab.to_s does take two arguments for passing in variables and a helper object. You can also affix the block right on to the class.

See Markaby::Builder for all of that.

A Note About instance_eval

The Markaby::Builder class is different from the normal Builder class, since it uses instance_eval when running blocks. This cleans up the appearance of the Markaby code you write. If instance_eval was not used, the code would look like this:

mab =
mab.html do
  mab.head { mab.title "" }
  mab.body do
    mab.h1 " has great deals"
puts mab.to_s

So, the advantage is the cleanliness of your code. The disadvantage is that the block will run inside the Markaby::Builder object’s scope. This means that inside these blocks, self will be your Markaby::Builder object. When you use instance variables in these blocks, they will be instance variables of the Markaby::Builder object.

This doesn’t affect Rails users, but when used in regular Ruby code, it can be a bit disorienting. You are recommended to put your Markaby code in a module where it won’t mix with anything.

The Six Steps of Markaby

If you dive right into Markaby, it’ll probably make good sense, but you’re likely to run into a few kinks. Why not review these six steps and commit them memory so you can really know what you’re doing?

1. Element Classes

Element classes may be added by hooking methods onto container elements:

div.entry do
  h2.entryTitle 'Son of WebPage'
  div.entrySection %{by Anthony}
  div.entryContent 'Okay, once again, the idea here is ...'

Which results in:

<div class="entry">
  <h2 class="entryTitle">Son of WebPage</h2>
  <div class="entrySection">by Anthony</div>
  <div class="entryContent">Okay, once again, the idea here is ...</div>

Alternatively you can define the class as an attribute on your element - see below.

2. Element IDs

IDs may be added by the use of bang methods:! do
  div.content! do
    h1 "A Short Short Saintly Dog"

Which results in:

<div id="page">
  <div id="content">
    <h1>A Short Short Saintly Dog</h1>

Alternatively you can define the ID as an attribute on your element - see below.

3. Validate Your XHTML 1.0 Output

If you’d like Markaby to help you assemble valid XHTML documents, you can use the html5, xhtml_transitional or xhtml_strict methods in place of the normal html tag.

html5 do
  head { ... }
  body { ... }

This will add the XML instruction and the doctype tag to your document (for xhtml_strict and xhtml_transitional). Also, a character set meta tag will be placed inside your head tag.

Now, since Markaby knows which doctype you’re using, it checks a big list of valid tags and attributes before printing anything.

>> div styl: "padding: 10px" do
>>   img src: "samorost.jpg"
>> end
InvalidHtmlError: no such attribute `styl'

Markaby will also make sure you don’t use the same element ID twice!

4. Escape or No Escape?

Markaby uses a simple convention for escaping stuff: if a string is an argument, it gets escaped. If the string is in a block, it doesn’t.

This is handy if you’re using something like RedCloth or RDoc inside an element. Pass the string back through the block and it’ll skip out of escaping.

div.comment { }

But, if we have some raw text that needs escaping, pass it in as an argument:

div.comment raw_str

One caveat: if you have other tags inside a block, the string passed back will be ignored.

div.comment do "_why"
  div.says "Torpedoooooes!"

The final div above won’t appear in the output. You can’t mix tag modes like that, friend.

5. Auto-stringification

If you end up using any of your Markaby “tags” as a string, the tag won’t be output. It’ll be up to you to add the new string back into the HTML output.

This means if you call to_s, you’ll get a string back.

div.title { "Rock Bottom" + span(" by Robert Wyatt").to_s }

But, when you’re adding strings in Ruby, to_s happens automatically.

div.title { "Rock Bottom" + span(" by Robert Wyatt") }

Interpolation works fine.

div.title { "Rock Bottom #{span(" by Robert Wyatt")}" }

And any other operation you might perform on a string.! \
  ['5.gets', 'bits', 'cult', 'inspect', '-h'].map do |category|
    link_to category
  join( " | " )

6. The tag! Method

If you need to force a tag at any time, call tag! with the tag name followed by the possible arguments and block. The CssProxy won’t work with this technique.

tag! :select, :id => "country_list" do
  countries.each do |country|
    tag! :option, country

If you wish to register your own, specialist, tags, you can install a TagHandler

Some other notes, so you aren’t confused:

On using different tagsets:

Because of the ways various frameworks sub-render templates, to use a different tagset in a rendered sub template, you may need to set it at the top of your sub-template:

self.tagset = Markaby::HTML5
# or Markaby::Transitional, Markaby::XHTMLStrict, Markaby::XHTMLFrameset

Note, this is only necessary if you were rendering, say, a one off page as html transitional but had the default engine as html5.

Defining attributes on elements

If you do not use the CssProxy (div.entry to define the class,! to define the ID), then you can pass a hash to your element to define any arbitrary attributes.

div id: "page-123", class: "entry" do
  div style: "display: inline-block;" do
    p "Have you noticed this book is basically written by a lunatic?"

Will result in

<div id="page-123" class="entry">
  <div style="display: inline-block;">
    <p>Have you noticed this book is basically written by a lunatic?</p>

If you pass a hash to your attribute definition, Markaby will expand the hash entries. This is useful for data attributes (for example, if you are using a Stimulus controller), or aria attributes. Any attributes will have underscores replaced with dashes when the hash is expanded.

div data: { controller: "something" } do
  div do
    h1(data: { something_target: "title" }) { "There goes my pickup" }

Will result in

<div data-controller="something">
    <h1 data-something-target="title">There goes my pickup</h1>

Custom elements and web components

If you are using the HTML5 tagset (which is the default), and your document has custom-elements defined, you can create those in the same way as standard elements.

Unlike standard elements, there is no validity checking for your attributes.

article do
  my_custom_panel variant: "primary" do
    p "Our careers are so over"

Results in

  <my-custom-panel variant="primary">
    <p>Our careers are so over</p>


Markaby is a work of immense hope by Tim Fletcher and why the lucky stiff. It is maintained by joho, spox, and smtlaissezfaire. Thank you for giving it a whirl.

Markaby is inspired by the HTML library within cgi.rb. Hopefully it will turn around and take some cues.

Patches from contributors:

aredridel (Aria Stewart - [email protected])

- Make exceptions inherit from StandardError (f259c0)