API to interact with BrandCAPTCHA http://www.pontamedia.com/en/brandcaptcha/

Simple captcha

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

A honeypot style captcha extension for ActiveRecord. Simple one-line inclusion in the model combined with a simple form field should trap the bad guys in the molasses.

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

Unity Captcha is a gem that use two levels of Captcha. First level is about Left Hemisphere: Logic and Math. Second level is about Right Hemisphere: Intuition and Drawing. This two levels functioning in complete harmony creates unity and this is the base design of this Captcha.

To help with keep the bots at bay this gem helps you easily add honeypots to forms and/or obfuscate your form field names

A Rails captcha gem that attempts to determine whether or not a user is human.

Captcha Client for YunPian.com

Captchator as Rack middleware, and helpers for sinatra.

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

A captcha that uses images instead of garbled text

Rails mountable engine, that provides captcha support

Simple Audio Extension to Simple Captcha

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

Generates and verifies ascii art captcha.

A simple and fast image captcha generator that uses opencv and memcached.

Block repetetive requests from logged_in users and shows captcha.

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

Captcha Gem for Rails, which generates captcha image by Rust.