Web Accessibility Testing

ALT Text/Text Alternative Testing

Definition

Alternative text accessibility means that when non-text elements (e.g., images, form controls, embedded objects, multimedia, players, etc.) are unavailable, they are replaced by alternative text that conveys the same information and provides the same functionality as the non-text element.

Why is this an accessibility issue?

Many users are unable to perceive graphic images that are embedded in a web page.  For these users, the information and function of those images is lost unless an alternate representation is provided.

Testing Methodology

  • Ensure that all <img> elements include an ALT attribute
  • Ensure that ALT attributes provide content and functionality (i.e., linking, focusability) equivalent to the <img>element
  • Avoid using background images for content or functionality
  • Ensure that images used for decoration only include empty ALT text (alt="")
  • Ensure that all embedded objects (e.g., multimedia, applets, Flash components, etc.) include appropriate alternative text when those objects are not available
  • Ensure that long text descriptions are provided for non-text elements that require detailed explanation
  • Pages with visual CAPTCHAs include CAPTCHAs that use a different modality

Tools

  • WAVE Toolbar (Errors, Features, and Alerts)
    • Places overlay on current page, revealing images without ALT text
  • Web Developer Toolbar (Images/Disable Images/All Images)
    • Hides embedded images, revealing ALT text
    • Hides background images
  • Web Developer Toolbar (Images/Display ALT Attributes)
    • Generates overlay with ALT text

Conformance

Non-text elements meet accessibility criteria if:

  • All images include an ALT attribute with an appropriate text alternative
  • All information contained in the non-text element is communicated to the user through a text alternative
  • All functionality contained in the non-text element is communicated to the user through a text alternative
  • Decorative images contain empty ALT text
  • Adjacent text and image ALT does not repeat, or "stutter"
  • No other barriers are presented by missing text equivalents