This plugin adds helpers for the YinXiangMa CAPTCHA API

A simple way to add zero friction captchas to Rails forms

Simple gem to add captcha or negative captcha to your Rails 3 application

Helps humankind with simpler captchas

Form protection with simple captcha calculations.

ZeroCaptcha allows companies to solve captchas with artificial intelligence software, which is faster than humans and very accurate

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

Generates Text Catpchas, that are 'nice' by my own personal definition!

ALTCHA is a free, open-source CAPTCHA alternative that protects your website from spam and abuse

Simple reverse captcha solution that consist in create a hidden field that should be always empty.

Captcha library which uses imagemagick to create captchas

Repackaged visualCaptcha's backend service, including translation and minor modification. Mainly for private use. Everything still belongs to original author: emotionLoop.

Ruby port of VIT AutoCaptcha

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

This version include two important page 'Contact' and 'Register' with the 'Math-Captcha' method submit for prevent hacker attack.

Russian Post tracking toolset, consisting tracking form bot (since Russian Post is too retarded for normal API) and captcha solver/recognizer.

HumanDetector is a friendly logic captcha for Rails the doesn't require any external system dependency (e.g. external captcha API connections). It uses a simple question that any 7 or more years old human can understand, but that a spambot will not be able to answer. This Gem supports Ruby v1.9.2 and Rails 3.0.x.

This is a Captcha gem for Rails Applications. It drawing captcha image with C code so it no dependencies.

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

ReCaptcha implements view helpers to generate ReCaptcha code, with the noscript counterpart, required methods that interface with the HTTP API for captcha verification, a DSL to generate a before_filter and the code to implement AJAX captcha validation.