SimpleCaptcha is the simplest and a robust captcha. Its implementation requires adding up a single line in views and in controllers/models. SimpleCaptcha is available to be used with Rails2.0 or above and also it provides the backward compatibility with previous versions of Rails.

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.

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

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

DeathByCaptcha allows you to solve captchas with manual labor

BrainBuster - a logic captcha for Rails

Rails extension for Cloudflare's Turnstile CAPTCHA alternative. This gem should work with Rails 6.x, 7.x, 8.x and with Faraday 1.x and 2.x.

Rack middleware Captcha verification using Recaptcha API.

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.

Despamilator is a plugin based spam detector designed for use on your web forms borne out of two annoyances: Spam being submitted in my web forms and CAPTCHAS being intrusive. Despamilator will apply some commonly used heuristics from the world of anti-spam to help you decide whether your users a...

Arithmetic Captcha

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

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Drop in feedback engine with customizable fields, and captcha available

RubyGem package for visualCaptcha's backend service

FerrumMCP is a browser automation server that implements the Model Context Protocol (MCP), enabling AI assistants to interact with web pages through a standardized interface. Features include navigation, form interaction, content extraction, screenshot capture, JavaScript execution, cookie manage...

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

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

This plugin adds helpers for the YinXiangMa CAPTCHA API

A captcha that uses images instead of garbled text