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A CAPTCHA is a type of test used to protects website services against use by automated programs that might abuse or otherwise take advantage of the service. The idea is to have a simple question that is easy for a human to answer, but difficult for a computer program. The standard technique is to ask users to type in text shown in an image. Typical applications include protecting registration and comment forms.
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Includes demonstrations, research papers, and news.
Users need to roll dice and answer the question to verify they are human with this free image based service. Provides a demo, FAQs and customization options.
Information about the CAPTCHA software for Drupal.
Protects websites and online services from spam. Respects privacy and works automatically.
A jQuery plugin that requires users to sketch the shape they see in order to submit a form.
A W3C Working Group Note explaining how CAPTCHAs can present a major obstacle to users who have limited vision or a learning disability such as dyslexia. This document examines a number of potential solutions and alternative systems.
An open source Java framework for captcha definition and site integration. Project information, documentation, issue tracker, and download.
Software which doesn't require entering alpha-numeric characters via a keyboard. Plugins for popular CMS software.
A captcha system that uses successful decodings to helps digitise books for online use. Background, and details on how to incorporate into a site. Source code in several languages, and plugins for popular blogging and CMS software.
Open source PHP script for generating image CAPTCHAs with audio alternatives. Includes documentation, a gallery and an online demonstration. [LGPL]
A source of simple textual CAPTCHA logic questions.
Explains how captcha features can keep spammers from signing up for certain accounts online, such as email or weblogs. Explains how the system can be circumvented as well.
Protects websites and online services from spam. Respects privacy and works automatically.
Information about the CAPTCHA software for Drupal.
Includes demonstrations, research papers, and news.
Software which doesn't require entering alpha-numeric characters via a keyboard. Plugins for popular CMS software.
A source of simple textual CAPTCHA logic questions.
A jQuery plugin that requires users to sketch the shape they see in order to submit a form.
Users need to roll dice and answer the question to verify they are human with this free image based service. Provides a demo, FAQs and customization options.
A captcha system that uses successful decodings to helps digitise books for online use. Background, and details on how to incorporate into a site. Source code in several languages, and plugins for popular blogging and CMS software.
A W3C Working Group Note explaining how CAPTCHAs can present a major obstacle to users who have limited vision or a learning disability such as dyslexia. This document examines a number of potential solutions and alternative systems.
An open source Java framework for captcha definition and site integration. Project information, documentation, issue tracker, and download.
Open source PHP script for generating image CAPTCHAs with audio alternatives. Includes documentation, a gallery and an online demonstration. [LGPL]
Explains how captcha features can keep spammers from signing up for certain accounts online, such as email or weblogs. Explains how the system can be circumvented as well.

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