Anti-spam protection for your website

Captchator as Rack middleware, and helpers for sinatra.

wxianfeng_simple_captcha is captcha for rails,modified from simple_captcha .

Block repetetive requests from logged_in users and shows captcha.

Captcha form Jike API

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

AntiCaptcha api ruby wrapper

A captcha that uses images instead of garbled text

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

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

It's a Rails Captcha Engine for Rails 3 applications.

Ruby port of VIT AutoCaptcha

Rails mountable engine, that provides captcha support

A gem to generate captcha pictures.

Due to many unrequited complaints to the recaptcha team with regard to its unreadability for real human users, this gem offers a more readable selection of captcha images.

Metabypass | Ruby-based easy implementation for solving any type of captcha by Metabypass

A simple and custom captcha for Rails3.

Antigate (Decode captcha service) wrapper for Ruby

Ruby wrapper for Yandex.Cleanweb