Fred’s Head from APH, a Blindness Blog

Fred’s Head, offered by the American Printing House for the Blind, contains tips, techniques, tutorials, in-depth articles, and resources for and by blind or visually impaired people. Our blog is named after the legendary Fred Gissoni, renowned for answering a seemingly infinite variety of questions on every aspect of blindness.

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Friday, May 21, 2010

Website Developers Can Use Accessible Text CAPTCHAs

A CAPTCHA is a test to tell humans and robots apart. You've probably used one before: identifying a string of letters from an image to show that you are human, rather than an automated "bot".

This site provides a web service to generate text-based CAPTCHAs, based on simple logic questions.

  • In the number 6272627, what is the 5th digit?
  • The colour in the list Wednesday, black, Elizabeth or stomach is?
  • The 2nd colour in arm, fifty six, pink and yellow is?

Image CAPTCHAs are inaccessible to visually impaired users, and depending on the level of letter distortion, sometimes quite difficult for fully able ones! An alternative audio test is often provided to address accessibility concerns, but this whole approach remains difficult to implement, awkward to style, and remains susceptible to automatic character recognition software.

This site provides a simple web service to generate text-based CAPTCHAs. These tell humans and robots apart by asking a simple logic question. These questions are aimed at a child's age of 7, so can be solved easily by all but the most cognitively impaired users. As they involve human logic, such questions cannot be solved by a robot.

Want to use such CAPTCHAs on your website? Visit http://textcaptcha.com.

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