Captchas

This is a technique for testing:

WCAG 2.0: Guideline 1.1 Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language. How to Meet 1.1.1 | Understanding 1.1.1

Overview

Captcha: If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.

Captcha.net provides images and audio files that act as passwords and this is how they describe the service “A Captcha is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't.”

google captcha

Example of a Google Captcha used for new accounts with option for listening to numbers in amongst other sounds.

recaptcha

Example of a reCAPTCHA from ReCAPTCAH main page, with option for listening to a sentence with noises.

For those who cannot see clearly, have difficulty reading misshapen letters and images or who cannot decipher the audio version, Captchas cause barriers. Gareth Heyes offers one solution to an accessible Captcha and Purple Dogfish has another accessible Captcha option.

Method

Manual testing is the only way to check that alternatives have been offered but often Webaim Wave (http://wave.webaim.org/) causes an alert as the Captcha may not be labelled or carry an alternative text (alt text) attribute.

Some social networking sites still use inaccessible Captchas, although some are now offering mobile phone alternatives or contact details. The American Foundation for the Blind discussed the issues in 2008 and the situation with log-ins is changing all the time as more people become aware of the issues.

Advice