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Sinatra is a DSL for quickly creating web-applications in Ruby with minimal effort:

# myapp.rb
require 'rubygems'
require 'sinatra'
get '/' do
  'Hello world!'

Run with ruby myapp.rb and view at localhost:4567

HTTP Methods

get '/' do
  .. show things ..

post '/' do
  .. create something ..

put '/' do
  .. update something ..

delete '/' do
  .. annihilate something ..


Routes are matched based on the order of declaration. The first route that matches the request is invoked.

Basic routes:

get '/hi' do

Route patterns may include named parameters, accessible via the params hash:

get '/:name' do
  # matches "GET /foo" and "GET /bar"
  # params[:name] is 'foo' or 'bar'
  "Hello #{params[:name]}!"

Route patterns may also include splat (or wildcard) parameters, accessible via the params[:splat] array.

get '/say/*/to/*' do
  # matches /say/hello/to/world
  params[:splat] # => ["hello", "world"]

get '/download/*.*' do
  # matches /download/path/to/file.xml
  params[:splat] # => ["path/to/file", "xml"]

Route matching with Regular Expressions:

get %r{/hello/([\w]+)} do
  "Hello, #{params[:captures].first}!"

Routes may include a variety of matching conditions, such as the user agent:

get '/foo', :agent => /Songbird (\d\.\d)[\d\/]*?/ do
  "You're using Songbird version #{params[:agent][0]}"

get '/foo' do
  # Matches non-songbird browsers

Static Files

Static files are served from the ./public directory. You can specify a different location by setting the :public option:

set :public, File.dirname(__FILE__) + '/static'

Views / Templates

Templates are assumed to be located directly under a ./views directory. To use a different views directory:

set :views, File.dirname(__FILE__) + '/templates'

Haml Templates

The haml gem/library is required to render HAML templates:

get '/' do
  haml :index

Renders ./views/index.haml.

Erb Templates

get '/' do
  erb :index

Renders ./views/index.erb

Builder Templates

The builder gem/library is required to render builder templates:

get '/' do
  content_type 'application/xml', :charset => 'utf-8'
  builder :index

Renders ./views/index.builder.

Sass Templates

The sass gem/library is required to render Sass templates:

get '/stylesheet.css' do
  content_type 'text/css', :charset => 'utf-8'
  sass :stylesheet

Renders ./views/stylesheet.sass.

Inline Templates

get '/' do
  haml '%div.title Hello World'

Renders the inlined template string.

Accessing Variables

Templates are evaluated within the same context as the route blocks. Instance variables set in route blocks are available in templates:

get '/:id' do
  @foo = Foo.find(params[:id])
  haml '%h1='

Or, specify an explicit Hash of local variables:

get '/:id' do
  foo = Foo.find(params[:id])
  haml '%h1=', :locals => { :foo => foo }

This is typically used when rendering templates as partials from within other templates.

In-file Templates

Templates may be defined at the end of the source file:

require 'rubygems'
require 'sinatra'

get '/' do
  haml :index


@@ layout
  = yield

@@ index
%div.title Hello world!!!!!

NOTE: Sinatra will automaticly load any in-file-templates in the source file that first required sinatra. If you have in-file-templates in another source file you will need to explicitly call +use_in_file_templates! on main in that file.

It's also possible to define named templates using the top-level template method:

template :layout do
  "%html\n  =yield\n"

template :index do
  '%div.title Hello World!'

get '/' do
  haml :index

If a template named “layout” exists, it will be used each time a template is rendered. You can disable layouts by passing :layout => false.

get '/' do
  haml :index, :layout => !request.xhr?


Use the top-level helpers method to define helper methods for use in route blocks and templates:

helpers do
  def bar(name)

get '/:name' do


Before filters are evaluated before each request within the context of the request and can modify the request and response. Instance variables set in filters are accessible by routes and templates.

before do
  @note = 'Hi!'
  request.path_info = '/foo/bar/baz'

get '/foo/*' do
  @note #=> 'Hi!'
  params[:splat] #=> 'bar/baz'


To immediately stop a request during a before filter or route use:


You can also specify a body when halting …

halt 'this will be the body'

Set the status and body …

halt 401, 'go away!'


A route can punt processing to the next matching route using the pass statement:

get '/guess/:who' do
  pass unless params[:who] == 'Frank'
  "You got me!"

get '/guess/*' do
  "You missed!"

The route block is immediately exited and control continues with the next matching route. If no matching route is found, a 404 is returned.

Configuration and Reloading

Sinatra supports multiple environments and reloading. Reloading happens before each request when running under the :development environment. Wrap your configurations (e.g., database connections, constants, etc.) in configure blocks to protect them from reloading or to target specific environments.

Run once, at startup, in any environment:

configure do

Run only when the environment (RACK_ENV environment variable) is set to :production.

configure :production do

Run when the environment (RACK_ENV environment variable) is set to either :production or :test.

configure :production, :test do

Error handling

Error handlers run within the same context as routes and before filters, which means you get all the goodies it has to offer, like haml, erb, halt, etc.

Not Found

When a Sinatra::NotFound exception is raised, or the response's status code is 404, the not_found handler is invoked:

not_found do
  'This is nowhere to be found'


The error handler is invoked any time an exception is raised from a route block or before filter. The exception object can be obtained from the 'sinatra.error' Rack variable:

error do
  'Sorry there was a nasty error - ' + env['sinatra.error'].name

Custom errors:

error MyCustomError do
  'So what happened was...' + request.env['sinatra.error'].message

Then, if this happens:

get '/' do
  raise MyCustomError, 'something bad'

You get this:

So what happened was... something bad

Sinatra installs special not_found and error handlers when running under the development environment.

Mime types

When using send_file or static files you may have mime types Sinatra doesn't understand. Use mime to register them by file extension:

mime :foo, 'text/foo'

Rack Middleware

Sinatra rides on Rack, a minimal standard interface for Ruby web frameworks. One of Rack's most interesting capabilities for application developers is support for “middleware” – components that sit between the server and your application monitoring and/or manipulating the HTTP request/response to provide various types of common functionality.

Sinatra makes building Rack middleware pipelines a cinch via a top-level use method:

require 'sinatra'
require 'my_custom_middleware'

use Rack::Lint
use MyCustomMiddleware

get '/hello' do
  'Hello World'

The semantics of use are identical to those defined for the Rack::Builder DSL (most frequently used from rackup files). For example, the use method accepts multiple/variable args as well as blocks:

use Rack::Auth::Basic do |username, password|
  username == 'admin' && password == 'secret'

Rack is distributed with a variety of standard middleware for logging, debugging, URL routing, authentication, and session handling. Sinatra uses many of of these components automatically based on configuration so you typically don't have to use them explicitly.


The Sinatra::Test module includes a variety of helper methods for testing your Sinatra app. Sinatra includes support for Test::Unit, test-spec, RSpec, and Bacon through separate source files.


require 'sinatra'
require 'sinatra/test/unit'
require 'my_sinatra_app'

class MyAppTest < Test::Unit::TestCase
  def test_my_default
    get '/'
    assert_equal 'My Default Page!', @response.body

  def test_with_agent
    get '/', :agent => 'Songbird'
    assert_equal 'You're in Songbird!', @response.body



Install the test-spec gem and require 'sinatra/test/spec' before your app:

require 'sinatra'
require 'sinatra/test/spec'
require 'my_sinatra_app'

describe 'My app' do
  it "should show a default page" do
    get '/'
    body.should.equal 'My Default Page!'



Install the rspec gem and require 'sinatra/test/rspec' before your app:

require 'sinatra'
require 'sinatra/test/rspec'
require 'my_sinatra_app'

describe 'My app' do
  it 'should show a default page' do
    get '/'
    @response.should be_ok
    @response.body.should == 'My Default Page!'




require 'sinatra'
require 'sinatra/test/bacon'
require 'my_sinatra_app'

describe 'My app' do
  it 'should be ok' do
    get '/'
    body.should == 'Im OK'

See Sinatra::Test for more information on get, post, put, and friends.

Command line

Sinatra applications can be run directly:

ruby myapp.rb [-h] [-x] [-e ENVIRONMENT] [-p PORT] [-s HANDLER]

Options are:

-h # help
-p # set the port (default is 4567)
-e # set the environment (default is development)
-s # specify rack server/handler (default is thin)
-x # turn on the mutex lock (default is off)



Besides Ruby itself, you only need a text editor, preferably one that supports Ruby syntax hilighting. VIM and Emacs are a fine choice on any platform, but feel free to use whatever you're familiar with.

Sinatra uses the Git source code management system. If you're unfamiliar with Git, you can find more information and tutorials on as well as Scott Chacon created a great series of introductory screencasts about Git, which you can find here:

First Time: Cloning The Sinatra Repo

cd where/you/keep/your/projects
git clone git://
cd sinatra
cd path/to/your_project
ln -s ../sinatra/

Updating Your Existing Sinatra Clone

cd where/you/keep/sinatra
git pull

Using Edge Sinatra in Your App

at the top of your sinatra_app.rb file:

$LOAD_PATH.unshift File.dirname(__FILE__) + '/sinatra/lib'
require 'sinatra'

get '/about' do
  "I'm running on Version " + Sinatra::VERSION

Contributing a Patch

There are several ways to do this. Probably the easiest (and preferred) way is to fork Sinatra on GitHub (, push your changes to your Sinatra repo, and then send Blake Mizerany (bmizerany on GitHub) a pull request.

You can also create a patch file and attach it to a feature request or bug fix on the issue tracker (see below) or send it to the mailing list (see Community section).

Issue Tracking and Feature Requests


Mailing List

If you have a problem or question, please make sure to include all the relevant information in your mail, like the Sinatra version you're using, what version of Ruby you have, and so on.

IRC Channel

You can find us on the Freenode network in the channel #sinatra (irc://

There's usually someone online at any given time, but we cannot pay attention to the channel all the time, so please stick around for a while after asking a question.

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