Accessible Captchas
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Introduction
CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHAs are tests to prove you are human and not a bot, such as picking out objects from a set of images, listening to a garbled audio or trying to pick out letters and numbers from distorted text.
CAPTCHAs are inherently not accessible by design. They rely on human senses and cognition which means that people with certain disabilities are unable to complete them.
What's the issue with CAPTCHAs?
The easiest way to explain the issues with CAPTCHAs is with examples.
Visual
Any CAPTCHA relying on sight, such as picking all the traffic light images, or writing the letters in a distorted text, are not accessible to people who are blind, are deaf-blind, have low vision or have a reading disability such as dyslexia.
Audio
Any CAPTCHA relying on audio, such as picking out a word in the middle of a distorted soundtrack, are not accessible to people who are deaf, hard of hearing or those who have audio processing disorders.
Maths challenge
Any CAPTCHA that relies on doing calculations, even those considered simple such as 1 + 2, are not accessible to some people with cognitive disabilities, learning disabilities or those who have anxiety.
Alignment challenges
Any CAPTCHA relying on aligning two images are not accessible to people with vision disabilities or motor disabilities.
Click to prove you're not a robot
Even having a checkbox CAPTCHA can be difficult for some people because if they can't click it, sometimes another more complicated CAPTCHA is triggered instead.
Accessible CAPTCHA
The best way to make CAPTCHA accessible is to remove it. Unless you have a large problem with spam then CAPTCHA is probably not needed. You can try using things like honeypots for form submission. These are hidden form fields that only bots can find. Or consider two factor authentication for creating accounts and logging into services.
If you must use CAPTCHA then you must provide multiple ways for people to attempt the CAPTCHA. This means that if people can't fill in a visual CAPTCHA due to a disability, they can attempt an audio CAPTCHA instead.
Even having two types of CAPTCHA does not make your site accessible for everyone. If using CAPTCHA is the only way to get to a certain part of a website or perform a specific action, then you also need to provide a way for people who can't get past the CAPTCHAs to get help.
WCAG Criteria
Other Resources
Page last updated: 28th June 2024