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>> A CAPTCHA is a distorted image of text or numbers that's commonly placed on forms in order to reduce spam. You'll often see it on registration forms and blog comment forms. The reason it's there is to tell humans and computers apart. A human has to type in what letters or numbers are seen. Spam bots are programs that automatically go out and fill out forms to submit spam. Since they're not humans and cannon see the images, they cannot read them. However there are some spam bots that can read clear images using visual character recognition technology.
That's why the images you are asked to transcribe on forms are so distorted looking. If they were clear and easy to read, spam bots might be able to get through. Of course, the fact that they are so hard to read is a big accessibility concern and they can't be used at all by blind or visually impaired people. A blind person cannot see the image at all. And someone with a serious visual impairment will likely not be able to read the image at all either. In these cases, these people won't be able to submit the form. And in some cases, they won't be able to use the site entirely if the site requires a registration in order to use all of its features.
There's not way to make CAPTCHA images accessible because you can't put alt text on them. If you did so, then the spam bots would simply read the alt text and fill that in and get through the form. One attempt at addressing the accessibility issues with CAPTCHA is to include a link to a recording of letters or numbers being spoken and ask the user to listen and transcribe what they hear. There are still serious accessibility problems with this however. The audio is just as jumbled as the images are, again, in order to prevent advanced programs from being able to recognize what is being spoken and get through.
And of course, an audio version does not help someone who has both vision and hearing impairments. An example of this type of system is online at reCAPTCHA.net. Let's see how it works. Go to the URL reCAPTCHA.net. ReCAPTCHA is a free CAPTCHA program that anyone can place on their site. It includes an audio backup by default. On the ReCAPTCHA website, click on the link what is ReCAPTCHA? An example of the types of CAPTCHA image is shown.
Underneath the images are three links. One to refresh the image if this particular one is too hard to read. The second is a link to an audio recording to hear instead. Click on that audio link. ( Indistinguishable digital voice ) >> That's a great example of how garbled most audio backups are on CAPTCHA systems.
There are no easy answers regarding CAPTCHA. The best thing to do, of course, is to never use it. There are other programming techniques that you can use to try to combat spam. Those are beyond the scope of this title, but there are many other options out there for you to investigate. If you must use CAPTCHA, you should provide both an audio version and an alternate contact method as a backup. The ReCAPTCHA system that we looked at online is a good option for when you have to use a CAPTCHA because it does have an audio backup, but even when using ReCAPTCHA or something similar, remember to include a phone number on your site so that users who still cannot get past the CAPTCHA can contact you for help.
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