Choosing a CAPTCHA for a commercial product

Chris Heilmann has posted a detailed list of the pros and cons of several different methods for creating CAPTCHAs in CAPTCHA Alternatives for a commercial product?

All of the methods mentioned have both advantages and problems. Often the drawbacks are related to accessibility. The very nature of how CAPTCHAs work makes it difficult to come up with a single method that is fully accessible.

I think offering alternative CAPTCHAs would be best for both accessibility and usability. But exactly how that would work and which CAPTCHA alternatives to use, I don’t know.

Posted on December 18, 2005 in Accessibility, Quicklinks


  1. Nice sum up, but the ultimate solution for replacing image based captchas is still lacking.

  2. One CAPTCHA alternative I’ve seen a few times for users with impaired vision is a very short audio clip. Basically an audio CAPTCHA. Doesn’t provide a totally comprehensive solution, but it does include more people.

  3. An alternative to CAPTCHAs I think is putting a simple random question in the form, e.g. ‘What is the name of the capital of France’ or something similar.

    Of course, having more than one question like that one being displayed randomly would be necessary.

  4. Hey Nick and Chris, did you even read my post? Both of these options are listed and there is an explanation what the problems with them are.

    Klevo, well, I don’t hold the final solution ransom, I’d really like to know, too. My guess is an interplay of several of those, however, the issue is that if you offer an accessible fallback this could also be exactly the leverage a hacker needs.

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