The Four Principles: POUR

WCAG is organized around four core principles. All accessibility requirements flow from these:

Perceivable

Information and user interface components must be presentable to users in ways they can perceive. This means:

  • Providing text alternatives for non-text content (images, charts)
  • Providing captions and alternatives for multimedia
  • Making content adaptable and distinguishable (contrast, resizable text)
TaskWCAG Requirements
Adding images to a syllabusAlt text for all meaningful images
Choosing text and background colors4.5:1 contrast ratio minimum
Recording a lecture videoSynchronized, accurate captions

Operable

User interface components and navigation must be operable. This means:

  • All functionality available from a keyboard
  • Users have enough time to read and interact with content
  • No content that causes seizures or physical reactions (flashing lights or rapidly moving images)
  • Users can navigate, find content, and determine where they are
TaskWCAG Requirements
Structuring a Word documentProper heading hierarchy (H1, H2, H3)
Creating hyperlinksDescriptive link text (i.e., "apply for financial aid," not "click here")

Understandable

Content and the operation of the user interface must be understandable. This means:

  • Text content is readable and understandable
  • Content appears and operates in predictable ways
  • Users are helped to avoid and correct mistakes
TaskWCAG Requirements
Writing form labelsClear, descriptive labels for all fields
Setting document languageLanguage set in document properties

Robust

Content must be robust enough to be interpreted reliably by a wide variety of user agents, including assistive technologies. This means:

  • Content works with current and future tools
  • Screen readers and other assistive technologies can access all content
TaskWCAG Requirements
Exporting to PDFTags and structure preserved for screen readers
Building a tableHeader rows identified, no merged cells