Seems like there’s been more talk about CAPTCHA lately (stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”). Most of us dislike the use of CAPTCHA in web forms. And all of us (I hope) can certainly agree that it’s poor in usability, and often times not accessible–even for any human user; see Top 10 Worst Captchas. Even so, it’s still way too common on the web. Damn spammers are forcing developers to implement this poor technique.
Fortunately, the collective intelligence of developers across the world have created many alternatives to CAPTCHA. Here are some great ideas from WebAIM’s article Spam-free accessible forms:
- Detect spam-like content within submitted form elements.
- Detect content within a hidden form element.
- Validate the submitted form values.
- Search for the same content in multiple form elements.
- Generate dynamic content to ensure the form is submitted within a specific time window or by the same user.
- Create a multi-stage form or form verification page.
- Ensure the form is posted from your server.
Here are some other articles about the (in)accessibility of CAPTCHA and other resolutions:
- CAPTCHA GOTCHA
- CAPTCHAs, CAPTCHAs everywhere
- Inaccessibility of CAPTCHA (W3C)
- Accessibility of CAPTCHA (Juicy Studio)
- CAPTCHA Killer
- Web Axe podcast on CAPTCHA
Example of impossible CAPTCHA: