Monday, November 19, 2007

Accessible CAPTCHA

Every voice is important, except for spammers.

CAPTCHA stands for "Completely Automated Public Turing test to tell Computers and Humans Apart". Here's one that claims to be accessible:reCAPTCHA.

It will be great to see those communities that understand the future is for everyone start using accessible CAPTCHAs. It is also just good business sense.


Greg K Nicholson said...

This doesn't seem to be accessible for deafblind users, as it relies on the ability to either see or hear.

davidb said...

Greg, excellent point. Any leads on CAPTCHAs that work for all?

Greg K Nicholson said...

Eric Meyer's WP-Gatekeepeer approaches the problem by requiring thought on the part of the user, rather than perception.

For example, challenges such as “What is Eric's first name?” or “What colour is an orange?” should be straightforward for a human user to solve, but aren't immediately obvious to robots.

The downside to this is that the challenges have to be maintained manually: eventually a robot will learn (or be taught) to solve each one; and the challenges can't be generated programmatically—if they could, they could also be solved programmatically.

It's also possible that people with cognitive disabilities could be excluded.

Another approach I've heard of is to include a hidden form field that spamming robots will tinker with (to try to circumvent some anti-spam measure), and to only accept a comment if that field is left untouched. I guess you'd have to make sure not to trap form-filling user aids.

David Bolter said...

Note that WebVisum is gaining popularity. It is a Firefox browser add-on that, among other things, can solve captcha images.

Jeff.Wallmer said...

reCAPTCHA is extremely painful to use. They have words almost impossible to read.
Furthemore 'badguys' have extremely cheap services to solve captcha 'offshore' - like this one
So accessible CAPTCHA is oxymoron :(

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