A simple CAPTCHA implementation for Rails 5+ based on RMagick.

A simple and custom captcha for Rails3.

Simple captcha based on plain text questions.

adds audio support to simple captcha

Simple lib to generate a math_captcha to prevent spammers in form. Supports localization.

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

Simple reverse captcha solution that consist in create a hidden field that should be always empty.

Captcha form Jike API

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

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...

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

ReCaptcha implements view helpers to generate ReCaptcha code, with the noscript counterpart, required methods that interface with the HTTP API for captcha verification, a DSL to generate a before_filter and the code to implement AJAX captcha validation.

Simple, easy captcha for Sinatra

Captcha Client for YunPian.com

A simple image captcha gem

simple stupid captcha

Rails mountable engine, that provides captcha support

MVC based Math, Logic Captcha

DeathByCaptcha allows you to solve captchas with manual labor

BrainBuster - a logic captcha for Rails