Serve - A Rapid Prototyping Framework for Web Applications

Serve is a small Rack-based web server that makes it easy to serve HTML, ERB, HAML, or Slim templates from any directory.

But Serve is much more than a simple web server.

Serve's primary purpose is to provide a rapid prototyping framework for Web applications (specifically Rails apps). It is designed to complement web application development and enforce a strict separation of concerns between designer and developer. Using Serve allows the designer to work in a separate prototype project, while the developer can work on the actual application and utilize resources from the prototype as needed. This allows the designer to focus on presentation and flow, while the developer can focus on implementation.

This “Design First” approach can help a designer identify and fix a large number of problems before a feature is ever touched by the developer. Once a feature has been completed in the prototype project it can also be estimated with a high degree of accuracy.

A Serve prototype can work much like the finished application and be virtually indistinguishable. The only difference being that state is not saved as a user clicks around.

Serve can be used alongside any Web development framework, but Rails developers will find it especially familiar. One way of thinking about Serve is that it is essentially a Rails application with only one part of the Rails MVC stack – the views. Serve basically allows you to have a separate project just for designing the views for the application. When views are ready, they can be copied over from the prototype to the application almost as is. This process is eased since Serve has full support for partials and layouts with either ERB or HAML. Serve can also handle SASS, Slim, Textile, and Markdown if the appropriate libraries are installed.


Serve is distributed as a Ruby gem and can be installed from the command prompt. Just type:

gem install serve

Some systems, like the Mac, may require that you type:

sudo gem install serve

If you are a Mac user and are new to the command prompt see:

Google “command prompt windows” if you are on a PC to find a simple tutorial.


Once the gem is installed the `serve` command will be available from the command prompt. To launch Serve, just type the command and press enter:


This will launch a simple web server which you can access from any web browser at the following address:


Once the server is going it will output a running log of its activity. To stop the server at any time, type CTRL+C at the command prompt. By default the serve command serves up files from the current directory. To change this behavior, `cd` to the appropriate directory before starting serve or pass the directory as the final parameter to the command:

serve project_directory

The `serve` command automatically binds to (localhost) and uses port 4000 by default. To serve files over a different IP (that is bound to your computer) or port specify those options on the command line:

serve 4000               # a custom port

serve        # a custom IP

serve   # a custom IP and port

For your convenience if the file “script/server” exists in the current directory the serve command will start that instead of launching a Ruby Web server. You can specify the environment that you want to start the server with as an option on the command line:

serve production         # start script/server in production mode

Creating a New Serve Project

For simple projects, you don't need to structure your files in a specific way. All ERB, Haml, and Sass files will be processed wherever they are found in the project root. But for more complex projects you may want to use Serve with a `` file so that you can take advantage of other Rack middleware and structure the project in a Rack compatible way.

To create a new Rack-based Serve project in the “mockups” directory, type the following on the command line:

serve create mockups   # create a new project in the mockups directory

This will create a new project with the following directory structure:

  +--              # Rack configuration file
  +-- compass.config         # Compass configuration file
  +-- public/                # Directories for static assets
  |    |
  |    +-- stylesheets/      # Compiled stylesheets
  |    |
  |    +-- images/
  |    |
  |    `-- javascripts/
  +-- sass/                  # Store Sass source files here
  |    |
  |    `-- application.sass  # Example Sass file for application
  +-- tmp/                   # Needed for Passenger (mod_passenger)
  |    |
  |    `-- restart.txt
  `-- views/                 # Store your ERB, Haml, etc. here
       +-- _layout.html.erb  # Example layout
       +-- hello.html.erb    # Example view
       `-- view_helpers.rb   # Example view helpers

If you would like to generate the project with a specific JavaScript framework you can do so with the -j flag:

serve create mockups -j prototype

Available frameworks are: jquery, jquery-ui, mootools, prototype, and scriptaculous.

The `serve create` command can be executed multiple times or on an existing project without negative consequences.

Upgrading a Compass Project to a Serve Project

If you are a Compass user you can convert an existing Compass project to a Serve project with the “convert” sub-command:

serve convert mockups

This will rename and move a number of files for you and will turn your Compass project into a Serve project.

Note that after upgrading a Compass project, you will no longer need to use the `compass watch` command to generate your stylesheets. Your stylesheets will be compiled on the fly with Serve.


In Serve layouts work a little differently than they do in Rails. Because there are no controllers to derive layout names from, Serve relies on the directory structure to determine the layout associated with a specific view. Serve layouts are stored in “_layout.erb” or “_layout.haml” files. Serve searches for a layout file in the same directory as the view. If it fails to find one there, it traverses up the directory tree searching each parent directory until it finds the “nearest” layout.

For example, assuming following directory structure:

A)      +-- _layout.erb
        +-- index.erb
        `-- about/
B)            +-- _layout.erb
              `-- index.erb

For “views/about/index.erb” Serve will use layout B. If layout B did not exist, Serve would go up the directory tree and discover layout A which it would use to render the view.

For “views/index.erb” Serve would immediately discover and use layout A because it is in the same directory.

So Serve searches up the directory tree for the nearest layout file, and uses that file to render the view. This is convenient because it allows you to structure your Serve project in a way that allows entire “branches” of to share the same layout and “branches” lower down can override the layout used.


Partials in Serve work much like they do in Rails. Prefix your partials with an underscore (“_”) and use the render helper method in your views to render the partial:

<%= render "footer" %>


<%= render "/shared/footer" %>

View Helpers

If you drop a file called “view_helpers.rb” in your views directory, you can define custom helpers for your Haml and ERB views. Just create a ViewHelpers module and define your helper methods there:

module ViewHelpers
  def custom_method
    "Request object: #{request.headers['user-agent']}"

Helpers have full access to the request and response objects so you can easily read and manipulate headers or do other fancy tricks.

Serve provides a number of stock helpers to make it easier for you to prototype Rails applications:

# Escape Helpers
html_escape(string)              # escape HTML in string
h(string)                        # alias for html_escape
json_escape(string)              # escape invalid JSON characters in string
j(string)                        # alias for json_escape

# Content Helpers
capture_erb(&block)              # Capture a block inside of a view or layout
content_for(symbol, &block)      # Capture a block and store it by symbol
content_for?(symbol)             # Has content been captured for symbol?
get_content_for(symbol)          # Retrieve content for symbol (equivalent to `yield symbol`)
set_content_for(symbol, string)  # Set content for symbol to string

# Flash Helpers
flash                            # fake flash for request

# Param Helpers
params                           # access params for request
boolean_param(key)               # retrieve value of a boolean param (true/false)

# Render Helpers
render(partial)                  # Render a partial

# Tag Helpers
content_tag(name, content, ...)  # a double HTML tag
tag(name, ...)                   # a single HTML tag
image_tag(src, ...)              # an HTML image tag
image(name, ...)                 # shorthand for standard image tag
javascript_tag(...)              # a javascript tag
link_to(name, href, ...)         # a link to name at href
link_to_function(name, ...)      # a link to a function
mail_to(email_address, ...)      # a mailto link

For more information, see:

File Types

Serve does special processing for files with following extensions:


Evaluates the document as Textile (requires the Redcloth gem)


Evaluates the document as Markdown (requires the Bluecloth gem)


Experimental support for ERB


Evaluates the document as Haml (requires the Haml gem)


Evaluates the document using the Slim template language (requires the Slim gem)


Evaluates the document as Sass (requires the Haml gem)


Evaluates the document as SCSS (requires the Haml gem)


Evaluates the document as if it is an e-mail message; the format is identical to a plain/text e-mail message's source


Redirects to the URL contained in the document

More Information

You can find more information about Serve, including a detailed Screencast, on the GitHub wiki:

Have questions? Feel free to ask them on the mailing list:


Serve is released under the MIT license and is copyright © 2007-2011 John W. Long and Adam I. Williams. Portions have been contributed by Robert Evans and others. A copy of the MIT license can be found in the LICENSE file.