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AFBAmerican Foundation®
for the Blind

Expanding possibilities for people with vision loss

Can CAPTCHAs Be Made Accessible?

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example of an inaccessible image captcha: the words

Lots of websites have a real and urgent need to keep bots and spammers off their sites. One partial solution is the CAPTCHA.

What Is a CAPTCHA, and Can It Be Accessible?

Really, a CAPTCHA is any technique that can be used to tell a computer (bot) from a human. But the most common technique is to put a fuzzy bunch of characters on the page and ask the user to type them into an edit field. A human, theoretically, can decipher the fuzzy characters, but a bot cannot. This has some obvious flaws in it, even if you've never seen these things (or didn't know what they were, more likely).

First, if you are a human who can't see very well, or can't type very well, can you do this? The CAPTCHA even keeps away people who don't think they have a visual impairment, just have normal trouble with tiny, fuzzy, low-contrast text. If you have to say "Wait, let me go get my glasses," you know someone who really has low vision is going to be stuck.

What about assistive technology? Can the CAPTCHAs be read by a screen reader? No. How about putting a civilized alt tag on the image of text? No. Remember, the sites who use them are trying to keep away bots. So, anything machine-readable would be easily defeated by the bots.

Some sites have put up an audible CAPTCHA. The idea is to hit a button or link, listen to some audio, and type what you hear into the box. The audio is made very hard to understand, a and there are usually several voices saying numbers and letters, so it is hard for a human to know what to type and what to ignore. This is intended to defeat the bots, of course, but it defeats humans, too. Users who don't have good hearing, don't have audio on their computers, or lack typing skill, are cut out, along with those in noisy environments.

So, is this really a bleak situation?

No, we have a solution. If you comment on this blog post, you'll see an accessible CAPTCHA in action.

How Does an Accessible CAPTCHA Work?

Here's how ours works—evil bots, go away, don't read this!

We have a teeny list of questions and answers. The questions have to be really easy, so that a user who has a reasonable ability to use this site would be able to answer the question. The answers have to be easy, and no ambiguous spelling options are allowed. For example, we can never have "good bye" as the answer, because there are 211 ways to spell it. (I made that number up.)

So, we might have:

Please type "hello" here.


Please put the word horse in the box.

We have to vary the structure of the sentence, so that a determined bot programmer cannot simply say to pull the word out of the quotes and put it into the box. And, we have to have enough of them that the bot can't put "horse" into the box and be correct every fifth time.

Advantages of This System Over the Image-of-Fuzzy-Text Approach

It can be made to be any color or any size by the user. So, someone with low vision can make it readable along with the rest of the site, no special technique or knowledge required.

The screen reader user hears the clue just like the rest of the site's text, and can read the clue word-by-word or character-by-character if necessary to see exactly what is wanted.

Users of braille displays sees the accessible CAPTCHA on the braille display just as they do any other text, making this technique work just as well for deaf-blind users as for any user.

In other words, the amount of knowledge, skill, visual acuity, and computer access for the CAPTCHA is the same as for the rest of the site.

Is This a Perfect Solution?

It is still an obstacle to some human users, in particular those who use screen readers and have low literacy skills. Some of our users don't know how to spell "senior" and they don't know how to get their screen readers to tell them the details. People for whom English is not their native language have also had trouble with our CAPTCHAs—we avoid using color names, as users sometimes interpret "Type the word 'blue'" as "Type the word that is blue," and are frustrated (and angry, as you might imagine).

And, we have to continually update our list of clues and answers, so the bots don't catch on. We have to test new pairs with users, so we can be sure we haven't inadvertently introduced complexity.

Please comment on the blog or post on the message boards, and see what you think of our little CAPTCHA!

Web Accessibility
Assistive Technology
There are currently 14 comments

Re: Can CAPTCHAs Be Made Accessible?

Great post. AFB definitely gets it right in my books when it comes to proving you're a human, and not a bot. Just a few months ago I created a journal on a site that lets users choose whether to have a text-based or a visual-only CAPTCHA. No audio alternative. That is one of the reasons I registered there.

Re: Can CAPTCHAs Be Made Accessible?

This has been a pain for me every time I have to post comments on sites for news

Re: Can CAPTCHAs Be Made Accessible?

Thank you. Thank you. Thank you. I really appreciate you writing this post. I am so annoyed with those verification screens I could literally scream! Just yesterday I was trying to sign up for my diversity advocacy group newsletter and I had to “listen” to the info but of course I could not understand a word the person was saying and I think my hearing is pretty good. I am going to keep this article handy and every time I come across websites that have an inaccessible verification screen I am going to e-mail their web designer this post. People need to understand how important this is.

What I am also noticing besides the “type what you see” and “type what you hear” is ones that say put in your blogger address. Since I blog for my employer and also for VisionAware I don’t really have “an address” and because of that I am not able to join in the conversation with other bloggers and post comments.

Again thank you so much.

Re: Can CAPTCHAs Be Made Accessible?

I'm glad you found the post useful! Yes, the inaccessible CAPTCHA is the bane of my existence, too.

I remember the first time I encountered one, so many years ago. A friend was trying to sign up for a service, and finally had to call his brother and have him do the sign-up for him. Of course, the brother couldn't just tell my friend what the characters were over the phone, because the Captcha has to be different each time.

I thought it was such a crazy, dumb thing and thought it would go away... no such luck. We have to show there is an alternative to this little eye exam, the need to keep the spam bots away is very real!

Re: Can CAPTCHAs Be Made Accessible?

Our college radio station had a captcha I asked to be made accessible and they did by having a random letter and numbers combination displayed. Our local public TV station had an inaccessible captcha and when I told them they recorded their own audio captcha that is clear to hear and works fine. They are not high traffic sites but it was very considerate of them to listen and respond. FireFox use to have an add-in Webvisum that would sometimes be able to interpret and paste the correct response in the clipboard. Not sure if Webvisum add-in still works.

Re: Can CAPTCHAs Be Made Accessible?


Your advocacy efforts are very encouraging. I feel better about reaching out to websites and telling them about this. I am glad you shared your success story.

Re: Can CAPTCHAs Be Made Accessible?

The WebVisum add-on for Firefox is still available as a method for solving visual captchas. In my experience, the Webvisum extension does an excellent job solving visual captchas. However, it is not always perfet. Audio captchas frustrate me because it is usually difficult or impossible to understand them. A text captcha such as the one utilized by AFB is the perfect solution in my book. I have seen text captchas on two other sites. Ideally, text captchas should be utilized on more sites for more equal access.

Re: Can CAPTCHAs Be Made Accessible?

Hello; I think I have some good news for our community. The blogging world has adopted the view that captchas are no longer best practices. The leaders are now recommending that people use a quality comment system like comment luv discuss or jet pack combined with a anti virus plug in like kismet. They recommend using email sign up forms that use email verification for confirming that you are human and not a spammer. And most of these comment systems offer an audio or non video option for those bloggers who still want to have a captcha. I am also finding that most all the comment forms being used on blogs come with form fields that are properly tagged so screen reader users can fill them out easily. The idea is that as a blogger you want comments and shares and you don't want to make it any harder for anyone to do this sighted or blind. Its like a lot of things, give people a good personal, professional, or financial reason to do it and they will get right on it. :) now just wish I could get regular website creators to get on the band wagon with eliminating captchas and more importantly adding alt tags and properly labeling all buttons. thanks for the post, Max

Re: Can CAPTCHAs Be Made Accessible?

Christa, soooo good to read this! The first time I came across a text capture was on VisionAware and I almost cried with delight! I could not believe the difference it made by enabling me to comment by following the simple verbal instruction Jaws was able to read, no problem, a web miracle!
My burning question is, how do I put text capture on my own blog, how does one find out the code or the technique to do this?
I hope you can advise me, I'd love to let other webmasters know, many thanks...

Re: Can CAPTCHAs Be Made Accessible?

Yes this is the thing i have from eye vision

Re: Can CAPTCHAs Be Made Accessible?

Thank you Crista for bringing this to public attention. I have always hated capchas and I don't think I have ever been able to decipher an audio capcha as they are so distorted. I've always loved the AFB capcha system, but I don't think I've ever seen it anywhere else. Thanks again!

Re: Can CAPTCHAs Be Made Accessible?

Since we are revisiting this topic, I want to share that I actually had two experiences with accessible verification screens recently on commercial websites. I clicked on the links that said “type what you hear” and I was actualy able to understand what was spoken. The person spoke clearly. There was not background noise at all. The voice said a couple of numbers that I had to type in the box. The difference was that some of the numbers were spoken a little faster than the others but not by that much. I was amazed! Someone out there is actually getting it right! Yeah!

Re: Can CAPTCHAs Be Made Accessible?


Re: Can CAPTCHAs Be Made Accessible?


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