A captcha that uses images instead of garbled text

Block repetetive requests from logged_in users and shows captcha.

Simple Audio Extension to Simple Captcha

Captchator as Rack middleware, and helpers for sinatra.

A simple and custom captcha for Rails3.

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

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

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

Arithmetic Captcha

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

adds audio support to simple captcha

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

Ruby wrapper for Yandex.Cleanweb

Wrapper for Captchabot.com

Antigate (Decode captcha service) wrapper for Ruby

A simple way to add zero friction captchas to Rails forms

Anti-spam protection for your website

Implements view helpers for the ASIRRA CAPTCHA system for Rails-based websites

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

simple stupid captcha