A captcha verification approach for Rails apps, directly integrated into ActiveRecord’s validation mechanism and providing helpers for ActionController and ActionView.

A gem to generate captcha pictures.

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.

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

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

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

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

Captcha Client for YunPian.com

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

This is a gem wrapper for tiny captcha in C with no dependencies.

Captcha-Plugin for Rails

Display and verify arcaptcha service 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

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

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

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

A plugin to make the process of creating a negative captcha in Rails much less painful

BrainBuster - a logic captcha for Rails