Making CAPTCHA Accessible

You’re most likely here because you need to make sure the CAPTCHA you use is accessible to people with disabilities.

You might have a specific problem, like:

  • whether to use CAPTCHA at all
  • how to make the particular CAPTCHA you have to use accessible
  • which type of CAPTCHA is the most accessible
  • how to provide CAPTCHA in alternative formats
  • whether an equally secure solution is available
  • how to avoid keyboard traps
  • how to provide user instructions in an accessible way

Perhaps you need a comprehensive list of likely issues with CAPTCHA accessibility – and how to address them. Or maybe you just want to ask a direct question and get a clear, expert response.

You’re in the right place.

OzWiki will tell you what you need to know to make CAPTCHA usable by site visitors with disabilities. The CAPTCHA section details 23 accessibility problems and how to address them, demonstrating compliance with 19 WCAG Level A success criteria and four Level AA success criteria.

As a subscriber, you’ll also be able to request further or more detailed information relating to your specific situation.

See an example

CAPTCHA is not provided in an alternative sensory modality

CAPTCHA is not provided in an alternative sensory modality

WCAG SC 1.1.1: Non-text Content

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed:

  • Controls, Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to WCAG 2.0 guideline 4.1 for additional requirements for controls and content that accepts user input.)
  • Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to WCAG 2.0 guideline 1.2 for additional requirements for media.)
  • Test: If non-text content is a test or exercise that would be invalid if presented in text, then text alternatives at least provide descriptive identification of the non-text content.
  • Sensory: If non-text content is primarily intended to create a specific sensory experience, then text alternatives at least provide descriptive identification of the non-text content.
  • 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.
  • Decoration, Formatting, Invisible: If non-text content is pure decoration, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.


See more errors for this SC


G144: Ensuring that the Web Page contains another CAPTCHA serving the same purpose using a different modality



The CAPTCHA used in the site relies on vision. An alternative to the CAPTCHA is not provided in an alternative sensory modality, such as audio.

Incorrect Example(s)

Example 1

Standard CAPTCHA with text 'If you are unable to view the images, please contact redacted'

Example 2

Security check requirement "Please type in the characters you see in the image below" - no other alternative


Ensure any CAPTCHAs are removed or an accessible audio version is provided. For more information on the inaccessibility of CAPTCHAs see: CAPTCHA: Inaccessible to Everyone and CAPTCHA: How to do it right (ie. don’t use CAPTCHA!).

As an alternative to CAPTCHAs, use a human test question, such as:

  • Is fire hot or cold?
  • Is grass green or blue?

Already a subscriber?

Log in!

Want access?


OzWiki is an accessible resource that provides best known methods to achieve A & AA level design and interaction for web content in areas such as Audio, Video, Link, Captcha, Maps, Navigation and more. These outlined accessibility errors, examples and solutions help you become 508 compliant by demonstrating associated WCAG 2.0 success criteria and techniques.

Gain access to more detailed information on all OzWiki categories for only $39/month by purchasing a subscription today! You can cancel your subscription at any time.