In web applications, Captcha is used to prevent spam/bot from getting into our applications, inbox or databases. It ensures that web application using by a real human. Here, we are going to implement Googles reCAPTCHA service in our rails application by using recaptcha gem.

Step1: Add captcha gem into Gemfile

gem "recaptcha", require: "recaptcha/rails"

Step2: Run bundler

bundle install

Step3: Overridden the create method of devise registration controller

class User::RegistrationsController < Devise::RegistrationsController
      
       def create
        #build the resource
        build_resource(sign_up_params)   
        #Verifying Captcha
        if verify_recaptcha(model: resource) 
          super
        else
          render 'new'
        end
      end
      #
      # Other line of Codes
    end

 Step4: To implement Googles reCAPTCHA we need a public and private key by registering on Google recaptcha account(URL: "https://www.google.com/recaptcha/admin")

Step5:  Now configure recaptcha like below...

Path:   config/initializer/recaptcha.rb

Recaptcha.configure do |config|
   config.public_key  = 'your public key'
   config.private_key = 'private key'
end

Step6: Modify the routes.rb like below...

Path: /config/routes.rb

devise_for :users, :controllers => {:registrations => "user/registrations"}

Step7: Display captcha in registration form

Path: app/views/devise/registrations/new

<%= recaptcha_tags %>