WebAIM - Web Accessibility In Mind

E-mail List Archives

Re: RE: Captchas

for

From: Peter Krantz
Date: Sep 21, 2006 7:10AM

On 9/21/06, Tim Harshbarger < <EMAIL REMOVED> > wrote:
>
> Darrel also makes a good point about not annoying the users.
> Interestingly, every article I have read about captchas (that did not
> focus on accessibility) tends to discuss the advantages and
> disadvantages from a site owner's or developer's point of view. I don't
> think I recall any of those articles taking a user perspective or
> discussing how captcha might impact a site's user base.
>

I agree. A while ago I wrote a proposal for an accessible captcha that
I evaluated through the personas described in Mark Pilgrim's Dive into
accessibility. It is available here:

http://standards-schmandards.com/index.php?2005/01/01/11

The fact is that most sites do not require a captcha. And if you do,
there is rarely a need for an advanced captcha. If you look at it from
the malevolent visitor's point of view you realize that there has to
be an incentive for them to create software to break the captcha.

Take spambots for example. I guess most of the applications that have
trouble with spambots (e.g. blogs, wikis) could have a simple text
based captcha like this:

Write 42 in this field: <field>

A spammer relies on mass volume distribution and it would be
inefficient to handle each victim site individually. The problem is
that most tools come with plugins for captchas that are more advanced
than necessary.

Regards,

Peter Krantz