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

Description of TinyCaptcha.

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

RedisCaptcha provides simple captcha that can be read by human.

Death by Captcha Ruby implementation (HTTP API)

NO LONGER MAINTAINED AND NOT RECOMMENDED, AS BOTS ARE ABLE TO RESOLVE CAPTCHAS BETTER THAN HUMANS.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.

Captcha based on encyrpting and decrypting user data by mathematical operation

This library can help you create a captcha in your terminal application, which may be damaged by a large influx of requests.

Description of RailsCaptcha.

you will get arithmatic sum with answer you just have to compare with ur user in controller

jQuery slide captcha system with jQuery & jQuery UI for Rails 3

Simple captcha image generator gem

RMagickCaptcha is a gem that implements captcha for using in Rails application.

Simple, easy captcha for Sinatra

Solve Media CAPTCHA Replacement

Forked from https://github.com/kares/simple_captcha

create captcha for api based project

Integrate the AreYouAHuman.com CAPTCHA alternative human verification into your Ruby/Rails application

MVC based Math, Logic Captcha

A very simple rack captcha middleware via captchator.com API