The quest for a bullet-proof but human-usable CAPTCHA continues. A couple of months ago, we talked about a CAPTCHA implementation that relies on human empathy to bypass, but for a couple of reasons, it might not be ideal for a lot of people. Now, the folks at Minteye have given us yet another option: slide-to-fit.
The idea is simple, and so is its usage. The user is presented with a nonsensical, twisted image. With a sliding bar, they can untwist the image so that it looks normal, at which point they'll be flagged as human and permitted to continue. As long as the basic premise is understood, this is a CAPTCHA implementation that shouldn't be difficult for anyone to use.
According to the developers, its slide-to-fit CAPTCHA has a success-rate of 94%, versus 76% for text-based offerings (a number that almost seems generous given how often I tend to fail them).
Minteye appears to be completely free for site owners to implement, and as the twisted images could be advertisements, potential revenue can be earned as well. It supports common Web languages like PHP, Java and ASP.NET, with plugins available for common content management systems, like WordPress, Drupal and phpBB.
As with most CAPTCHA implementations, I'm skeptical of just how useful this one will prove to be. In my mind, the empathy-based solution we talked about months ago would have the better chance of going unbeaten by PCs, as it shouldn't be too difficult in theory for a computer to tell the difference between a twisted image and a clean one. Nonetheless, it is a solution that's easy to understand, so it has that going for it.