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

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

A captcha that uses images instead of garbled text

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

Rails mountable engine, that provides captcha support

Quick little arithmetic plain-text captcha

This is mt first gem

This plugin adds helpers for the YinXiangMa CAPTCHA API

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

NO LONGER MAINTAINED AND NOT RECOMMENDED, AS BOTS ARE ABLE TO RESOLVE CAPTCHAS BETTER THAN HUMANS. Based on Login Attempts check if captcha is necessary. It stores a permanent cookie and uses a table for tracking login requests.

Helps humankind with simpler captchas

Form protection with simple captcha calculations.

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

My version of SimpleCaptcha

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 gem wrapper for tiny captcha in C with no dependencies.

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.

Death by Captcha Ruby implementation (HTTP API)

这是一个验证码生成器。基于rucaptcha。本人只是将他的源码拉下来。为我的网站进行适配。因为我不使用sesion.id

Captcha based on encyrpting and decrypting user data by mathematical operation