Saturday, November 26, 2005

CAPTCHA Accessibility Issues

CAPTCHA - What are the Alternatives?

In a very interesting document published by the working group over at W3C, it was discussed in detail how CAPTCHA's are very bad for accessibility.

In case you don't recall, CAPTCHA is that nice acronym for the terribly long phrase "Completely Automated Public Turing test to Tell Computers and Humans Apart". Yes, it's much easier to say CAPTCHA. A Turing test is something that many websites use nowadays to verify that the person filling in a log-in form, or posting on a message board or blog is actually a person - not a spamming program. Picture one of those little images with letters all crunched together, skewed this way and that, and you have to type what it says into the little input box nearby to enter.

You know, I have a confession to make. I have a turing test active to post to the comments for this blog. By default, it also gives me one of those darn things every time I edit a post of my own, or create one. I probably enter the letters wrong at least 1 out of every 5 times. (And that's being nice to myself.) The document points out:

This type of visual and textual verification comes at a huge price to users who are blind, visually impaired or dyslexic. Naturally, this image has no text equivalent accompanying it, as that would make it a giveaway to computerized systems. In many cases, these systems make it impossible for users with certain disabilities to create accounts, write comments, or make purchases on these sites, that is, CAPTCHAs fail to properly recognize users with disabilities as human.

I think that summarizes it quite well. They are not good for accessibility. And if:

many of the systems can be defeated by computers with between 88% and 100% accuracy, using optical character recognition.

is true... then why are we using them? But what are the alternatives. Some were suggested, but most had their own set of accessibility problems also. One was the idea of logic puzzles instead -- but that would not meet accessibility standards for people with mental / cognitive disabilities. Another was sound based -- but that disqualifies for a number of reasons (lack of a sound card, poor or no hearing, etc..).

In the end, the working group suggests that the CAPTCHA's stick around for websites that have users in the millions, but not for those with a small user base (i.e., most blogs). For smaller sites, spam-filering and heuristic checks were suggested in the place of CAPTCHA's. I don't know about you, but I've decided to turn my CAPTCHA off.


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