• Media Type Web > Forms
  • State Active
  • Advisory No

A CAPTCHA is a method used to tell computers and humans apart. This typically consists of an image that contains deliberately-blurred text that only a human could read. The text is then typed into an edit field to validate the form submission, which most commonly serves to create a user account. Because this CAPTCHA uses an image whose purpose would be nullified if it contained equivalent alternative text that could be captured programmatically, CAPTCHAs can be difficult or impossible for users of assistive technology to complete. This would effectively prevent users who are blind or disabled from creating accounts on and utilizing that web property.

Compliant Example

A CAPTCHA exists and a link is provided directly before the CAPTCHA indicating "Can't
see this image?". When the link is activated, an audio CAPTCHA plays and focus is
positioned in the edit field to input the characters that are announced in the audio.

Non-Compliant Example

A CAPTCHA is used requiring visual affirmation of graphical text to be entered in order to
advance in an application or form.  There is no alternative provided for the CAPTCHA.

Add an alternative version of the CAPTCHA that uses a different sense such as an audible version of the CAPTCHA content. In addition, make sure the alternative is made prominently available and is implemented in an accessible way. For example, for an audio CAPTCHA provide a link to play the audio, and focus the edit field where the characters must be typed. The audio must be audible or else it won't be usable by users who are blind or visually impaired.

The visual CAPTCHA should continue to be used to facilitate use by people who are deaf or hard of hearing

Some organizations and groups provide alternative solutions to CAPTCHA. to Tell Computers and Humans Apart). If such a solution is implemented, developers must ensure that keyboard access and textual alternatives are in place for full access by users with disabilities and function with assistive technology. All CAPTCHAs will be inaccessible to some people even though that ask for simple math problems or everyday questions.

The article In Search of the Perfect Captcha explores the different types of Captcha and various alternatives. Ultimately a solution that does not require a CAPTCHA is best for accessibility, however, due to complexity of the issue all that is correctly required is to provide a CAPTCHA or CAPTCHAs that do not rely on the same sense such as sight.

Organization Standards

  • § 508-1194.22 Web Sites and Applications
    • (a) Text equivalent of non-text items
    • (n) Ensure electronic forms are accessible
  • Section 508 and 255 (Revised 2017)
    • Chapter 3: Functional Performance Criteria
      • 302.2 With Limited Vision
      • 302.1 Without Vision
  • WCAG 2.0 Level A
    • 1.1.1 Provide text alternatives for all non-text content
  • WCAG 2.1 Level A
    • 1.1.1 Non-text Content

Other Mapped Standards

  • § 508-1194.21 Software Applications and Operating Systems
    • (d) Information about a user interface element must be textually available
    • (l) Ensure usability of electronic forms
  • § 508-1194.22 VA Testing Checklist - Web Sites and Applications
    • (n) When electronic forms are designed to be completed on-line, the form shall allow people using assistive technology to access the information, field elements, and functionality required for completion and submission of the form
      • (n.8) Are there accessible alternatives provided for security measures like CAPTCHA?
  • § 508-1194.31 Functional performance criteria
    • (a) Ensure access for blind and visually impaired
    • (b) Ensure access for low vision users
  • 47 CFR 14. Advanced Communication Services
    • 47 CFR 14.21 Performance Objectives
      • (b) Accessible
        • (b)(1) Input, control, and mechanical functions shall be locatable, identifiable, and operable
          • (b)(1)(i) Operable without vision
        • (b)(2) All information necessary to operate and use the product
          • (b)(2)(i) Availability of visual information
  • BITV 2.0 (Priority I)
    • 1.1.1 Nicht-Text-Inhalte
  • Baseline Tests for Software & Web Accessibility (v2.0.2 2017)
    • 7. Images
  • DHS - Section 508 Compliance Test Process for Application (v 4.0)
    • 2.2. Web: Images
      • 2.2 E. A CAPTCHA image ALT does not describe its purpose
    • 15. Web: Alternative (Accessible) Version
      • 15 A. An alternative page does not contain equivalent information as the primary page
  • EN 301 549 v3.2.1
    • Chapter 4: Functional Performance
      • 4.2 Functional Performance Statements (FPS)
        • 4.2.1 Usage without vision
        • 4.2.2 Usage with limited vision
    • Chapter 9: Web
      • 9.1 Perceivable
        • 9.1.1 Text alternatives
          • 9.1.1.1 Non-text content
  • HHS HTML 508 Checklist (2019)
    • Section K: Sites containing common elements / dynamic content
      • K8 Are CAPTCHA interfaces exit disclaimer icon able to be used with keyboard alone and assistive technology? Ability to tell the clue and successfully enter and authenticate
  • JIS X 8341-3: 2004 - Technical Standards Subpart 5
    • 5.6 (b) Use fonts which are easy to read.
  • KWCAG
    • 1-1 - Provide a text alternative for all non-text content
      • 1-1-1 - Provide a text alternative for all non-text content
  • Telecommunications Act Accessibility Guidelines
    • 1193.41 Input, control, and mechanical functions.
      • (a) Operable without vision. Provide at least one mode that does not require user vision.
    • 1193.43 Output, display, and control functions.
      • (a) Availability of visual information. Provide visual information through at least one mode in auditory form.
  • WCAG 1.0 Priority 1
    • 01.1 Lack of textual equivalents for non-text elements.
  • WCAG 2.0 Level A & AA Baseline
    • 6. Images
  • WCAG 2.1 Level A & AA Baseline
    • 6. Images
  • WCAG 2.2 Level A
    • 1.1.1 Non-text content
  • WCAG 2.2 Level A & AA Baseline
    • 6. Images

  • Severity

    10 (red)
    in range of 1 to 10

  • Noticeability

    5 ()
    in range of 1 to 10

  • Tractability

    3 ()
    in range of 1 to 10