SimpleCaptcha is the simplest and a robust captcha plugin. Its implementation requires adding up a single line in views and in controllers/models. SimpleCaptcha is available to be used with Rails 3 or above and also it provides the backward compatibility with previous versions of Rails.


  • Zero FileSystem usage(secret code moved to db-store and image storage removed).
  • Provides various image styles.
  • Provides three level of complexity of images.
  • Works absolutely fine in distributed environment(session and db based implementation works fine in distributed environment).
  • Implementation is as easy as just writing a single line in your view. "<%= show_simple_captcha %>" within the 'form' tags.
  • Flexible DOM and CSS handling(There is a separate view partial for rednering SimpleCaptcha DOM elements).
  • Automated removal of 1 hour old unmatched simple_captcha data.



gem "loyal-simple_captcha", :require => "simple_captcha"


gem 'loyal-simple_captcha', :require => 'simple_captcha', :git => 'git://github.com/blogsoso/simple-captcha.git'


After installation, follow these simple steps to setup the plugin. The setup will depend on the version of rails your application is using.

rails generate simple_captcha

rake db:migrate


===Controller Based

Add the following line in the file "app/controllers/application.rb"

ApplicationController < ActionController::Base include SimpleCaptcha::ControllerHelpers end

In the view file within the form tags add this code

<%= show_simple_captcha %>

and in the controller's action authenticate it as

if simple_captcha_valid? do this else do that end

===Model Based

In the view file within the form tags write this code

<%= show_simple_captcha(:object=>"user") %>

and in the model class add this code

class User < ActiveRecord::Base apply_simple_captcha end

====FormBuilder helper

<%= form_for @user do |form| -%> ... <%= form.simple_captcha :label => "Enter numbers.." %> ... <% end -%>

====Validating with captcha NOTE: @user.valid? will still work as it should, it will not validate the captcha code.


====Saving with captcha NOTE: @user.save will still work as it should, it will not validate the captcha code.


===Formtastic integration SimpleCaptcha detects if your use Formtastic and appends "SimpleCaptcha::CustomFormBuilder".

<%= form.input :captcha, :as => :simple_captcha %>

==Options & Examples ===View Options

  • label - provides the custom text b/w the image and the text field, the default is "type the code from the image"

  • object - the name of the object of the model class, to implement the model based captcha.

  • code_type - return numeric only if set to 'numeric'

===Global options

  • image_style - provides the specific image style for the captcha image. There are eight different styles available with the plugin as... 1) simply_blue 2) simply_red 3) simply_green 4) charcoal_grey 5) embosed_silver 6) all_black 7) distorted_black 8) almost_invisible Default style is 'simply_blue'. You can also specify 'random' to select the random image style.

  • distortion - handles the complexity of the image. The :distortion can be set to 'low', 'medium' or 'high'. Default is 'low'.

Create "rails_root/config/initializers/simple_captcha.rb"

SimpleCaptcha.setup do |sc| # default: 100x28 sc.image_size = '120x40'

# default: 5
sc.length = 6

# default: simply_blue
# possible values:
# 'embosed_silver',
# 'simply_red',
# 'simply_green',
# 'simply_blue',
# 'distorted_black',
# 'all_black',
# 'charcoal_grey',
# 'almost_invisible'
# 'random'
sc.image_style = 'simply_green'

# default: low
# possible values: 'low', 'medium', 'high', 'random'
sc.distortion = 'medium'


You can add your own style:

SimpleCaptcha.setup do |sc| sc.image_style = 'mycaptha' sc.add_image_style('mycaptha', [ "-background '#F4F7F8'", "-fill '#86818B'", "-border 1", "-bordercolor '#E0E2E3'"]) end

You can provide the path where image_magick is installed as well:

SimpleCaptcha.setup do |sc| sc.image_magick_path = '/usr/bin' # you can check this from console by running: which convert end

You can provide the path where should be stored tmp files. It's usefull when you dont have acces to /tmp (default directory)

SimpleCaptcha.setup do |sc| sc.tmp_path = '/tmp' # or somewhere in project eg. Rails.root.join('tmp/simple_captcha').to_s, make shure directory exists end

===How to change the CSS for SimpleCaptcha DOM elements? You can change the CSS of the SimpleCaptcha DOM elements as per your need in this file. /app/views/simple_captcha/_simple_captcha.erb

===View's Examples ====Controller Based Example

<%= show_simple_captcha %>

<%= show_simple_captcha(:label => "human authentication") %>

====Model Based Example

<%= show_simple_captcha(:object => 'user', :label => "human authentication") %>

====Model Options

  • message - provides the custom message on failure of captcha authentication the default is "Secret Code did not match with the Image"

  • add_to_base - if set to true, appends the error message to the base.

=====Model's Example

class User < ActiveRecord::Base apply_simple_captcha end

class User < ActiveRecord::Base apply_simple_captcha :message => "The secret Image and code were different", :add_to_base => true end


simple_captcha: message: default: "Secret Code did not match with the Image" user: "The secret Image and code were different"

==Who's who?

Enjoy the simplest captcha implementation.

Author: Sur

Blog: http://expressica.com

Contact: [email protected]

Plugin Homepage: http://expressica.com/simple_captcha

Plugin update for rails 3: http://github.com/blogsoso

Any feedback/comment/issue/donation is welcome!