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SimpleCaptcha is available to be used with Rails 3 + 4 or above and also it provides the backward compatibility with previous versions of Rails.

reCAPTCHA was too much for us, so we created this. Simplest captcha ever.

Unobtrusive, flexible and simple spam protection for Rails applications using honeypot strategy for better user experience.

Captcha-Plugin for Rails

Despamilator is a plugin based spam detector designed for use on your web forms borne out of two annoyances: Spam being submitted in my web forms and CAPTCHAS being intrusive. Despamilator will apply some commonly used heuristics from the world of anti-spam to help you decide whether your users a...

Rack middleware Captcha verification using Recaptcha API.

RubyGem package for visualCaptcha's backend service

DeathByCaptcha allows you to solve captchas with manual labor

LoyalSimpleCaptcha is available to be used with Rails 3 or above and also it provides the backward compatibility with previous versions of Rails.

Description of TinyCaptcha.

Captcha based on encyrpting and decrypting user data by mathematical operation

Captchator as Rack middleware, and helpers for sinatra.

Merb plugin that provides resource access rate limits and captcha'ing

Death by Captcha Ruby implementation (HTTP API)

RedisCaptcha provides simple captcha that can be read by human.

A library to make creating negative captchas less painful

Implementation of captcha (Completely Automated Public Turing-Test to Tell Computers and Humans Apart) that is both easy to use and easy to customize/extend.

Anti Captcha is an automated CAPTCHA solving service

This gem enable to use Captchme. Anti spam, Monetize captcha and Audience qualification