CAPTCHAs and their accessibility barriers
CAPTCHA is an acronym for “Completely Automated Public Turing Test, to Tell Computers and Humans Apart.” Websites use CAPTCHA tests to prevent bots from spamming and spreading viruses on their platforms. We will briefly cover the pros and cons of five types of CAPTCHA tests: visual, audio, logic, movement/game and non-interactive tests.
Problems of Accessibility
The most common CAPTCHA is a visual test in which users have to type a word or character that correlates to an image that appears on the screen. The text is distorted to prevent bots from reading it, but it can be confusing for the average user. Since the test relies on a distorted image, people who are blind, visually impaired or dyslexic may not be able to pass the test.
The alternative to a visual CAPTCHA test is an audio test. In this scenario, the sound output is distorted to avoid abuse by “bots” or other programs. The distorted audio clips can be unintelligible, even for people with good hearing. It can also be hard to determine whether the CAPTCHA wants a number to be entered or a word.
Furthermore, the visual and audio tests are originally in english, making the test even harder for non-english speakers.
Lastly, there are CAPTCHA tests that are logic based and others that are based on movement/games. The logic based test is the hardest CAPTCHA test for people with learning or cognitive disabilities. The game version is harder and more time consuming to create for developers. Developing a game CAPTCHA requires different inputs, such as mouse, keyboard, touch screen and even screen readers, with the last one more prone to bot abuse.
Non-Interactive approaches are the most accessible option because they don’t rely on user interaction. Non-Interactive approaches work behind the scenes to collect a user’s data or force the computer to process various tasks. The downside is they might slow hardware performance, need constant analysis of the data, trigger a false alarm or invade user privacy because they depend on user information.
Conclusion
There are pros and cons to all CAPTCHAs. When using a CAPTCHA it is necessary to analyse its potential impacts alongside the project scope. A solution might be implementing two rounds of CAPTCHAs. First a non-interactive test. If this test comes back with an alarm for bot behavior, it will trigger a second CAPTCHA that is interactive.
What to take into consideration when choosing a CAPTCHA:
- Don’t force users beyond what is necessary to keep the site secure.
- Choose the low effort approach. Less interactivity means more accessibility. Non-interactive approaches are the best because these pose no accessibility challenges. They do, however, expose the user to the collection of personal data.
- If you choose to use an interactive CAPTCHA, provide a couple versions. Providing multiple versions of a CAPTCHA attends to different disabilities.
- The use of third parties to verify the authenticity of an access attempt will increase security in exchange for user’s private information.
To learn more about the inaccessibility of CAPTCHAs, visit the W3C website.
