Helpers for the reCAPTCHA API

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

reCAPTCHA was too much for us, so we created this. Simplest captcha ever.

BrainBuster - a logic captcha for Rails

ActsAsTextcaptcha provides spam protection for Rails models with text-based logic question captchas. Questions are fetched from Rob Tuley's textcaptcha.com They can be solved easily by humans but are tough for robots to crack.

A Google-style captcha for enterprise Rails apps

Captcha form Jike API

A smart captcha library

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