The Web Content Accessibility Guidelines (WCAG) are a set of guidelines developed to make web content more accessible to people with disabilities, ensuring inclusivity for a wide range of users. A website should satisfy the following WCAG 2.0 Level AA guidelines under each principle (Perceivable, Operable, Understandable, and Robust):
1. Perceivable
- Text Alternatives: Provide text alternatives for all non-text content (e.g., images, icons) so that it can be rendered by assistive technologies like screen readers.
- Captions and Audio Descriptions: For pre-recorded video content, captions should be provided, and audio descriptions should be available for significant visual information.
- Color Contrast: Ensure that text and images of text have a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text.
- Adaptable Content: Content should be adaptable for different display modes (e.g., responsive design), allowing it to be presented in a way that is accessible without loss of information or structure.
- Text Resizing: Text should be resizable up to 200% without affecting readability or usability.
2. Operable
- Keyboard Accessibility: All interactive elements should be operable via keyboard alone, without requiring a mouse.
- Enough Time: Users should be provided with adequate time to read and interact with content, especially if there are timed interactions or sessions.
- Seizure Prevention: Avoid flashing content that might trigger seizures. Specifically, content should not flash more than three times in any one second.
- Navigable Content: Provide ways for users to navigate, find content, and determine where they are, such as meaningful headings, landmarks, and page titles.
3. Understandable
- Readable Text: Use clear and simple language to make the text understandable, especially for instructions, forms, and other critical content.
- Predictable Navigation: Content should operate predictably. For example, links should not open new windows without warning, and user input shouldn’t cause unexpected context changes.
- Input Assistance: Forms and input fields should provide labels, instructions, and error identification to help users understand how to interact with them and correct any mistakes.
4. Robust
Use of Semantic HTML: Elements should be coded to follow proper HTML semantics, ensuring a logical structure that aids both assistive technologies and search engines.
Compatibility with Assistive Technology: Ensure content is compatible with current and future assistive technologies. This involves using standard HTML and ARIA attributes where necessary, so screen readers and other assistive tools can interpret content correctly.
Level AA Success Criteria under Perceivable
- Text Alternatives (Guideline 1.1)
- 1.1.1 Non-text Content (Level A): Provide text alternatives for non-text content.
- Time-based Media (Guideline 1.2)
- 1.2.1 Audio-only and Video-only (Prerecorded) (Level A)
- 1.2.2 Captions (Prerecorded) (Level A)
- 1.2.3 Audio Description or Media Alternative (Prerecorded) (Level A)
- 1.2.4 Captions (Live) (Level AA)
- 1.2.5 Audio Description (Prerecorded) (Level AA)
- Adaptable (Guideline 1.3)
- 1.3.1 Info and Relationships (Level A): Ensure information, structure, and relationships can be programmatically determined.
- 1.3.2 Meaningful Sequence (Level A)
- 1.3.3 Sensory Characteristics (Level A)
- Distinguishable (Guideline 1.4)
- 1.4.1 Use of Color (Level A)
- 1.4.2 Audio Control (Level A)
- 1.4.3 Contrast (Minimum) (Level AA)
- 1.4.4 Resize Text (Level AA)
- 1.4.5 Images of Text (Level AA)
Level AAA Success Criteria
- Time-based Media (Guideline 1.2)
- 1.2.6 Sign Language (Prerecorded) (Level AAA)
- 1.2.7 Extended Audio Description (Prerecorded) (Level AAA)
- 1.2.8 Media Alternative (Prerecorded) (Level AAA)
- 1.2.9 Audio-only (Live) (Level AAA)
- Distinguishable (Guideline 1.4)
- 1.4.6 Contrast (Enhanced) (Level AAA)
- 1.4.7 Low or No Background Audio (Level AAA)
- 1.4.8 Visual Presentation (Level AAA)
- 1.4.9 Images of Text (No Exception) (Level AAA)
Conformance Level
Level A (Minimum) – Basic accessibility, addressing the most critical issues.
Level AA (Mid-range) – Addresses broader and more complex accessibility barriers, making content usable for a larger audience.
Level AAA (Highest) – The most accessible standard, often used for specialized content as not all websites can meet these stringent requirements.
Key Areas in WCAG Accessibility Testing
Text Alternatives for Non-Text Content:
All images, buttons, and other non-text elements should have alternative text (alt text) so screen readers can describe them.
Keyboard Accessibility:
The website should be navigable via keyboard alone, ensuring users can interact without relying on a mouse.
Color and Contrast:
Sufficient contrast between text and background colors (WCAG recommends a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text) to ensure readability for users with visual impairments.
Text Resizing and Responsive Design:
Users should be able to resize text up to 200% without losing content or functionality, ensuring readability across devices and viewports.
Content Structure and Navigation:
Proper use of HTML structure (e.g., headings, lists) and ARIA (Accessible Rich Internet Applications) roles to make navigation easier for screen reader users.
Multimedia Accessibility:
Provide captions, transcripts, and audio descriptions for video and audio content.
Focus Indicators:
Ensure visible focus indicators, which show users where they are on the page, especially useful for keyboard and screen reader users.
Error Identification and Suggestions:
Forms should provide clear error messages and guidance to users for correction, with programmatically indicated input fields.
Tools for WCAG Accessibility Testing
Several tools can be used to conduct accessibility testing based on WCAG standards:
- WAVE (Web Accessibility Evaluation Tool): Allows for quick WCAG checks by highlighting accessibility issues visually on web pages.
- AXE by Deque: A widely used open-source tool for identifying accessibility issues, often integrated as a browser extension.
- Lighthouse (Chrome DevTools): Provides an accessibility score and suggests improvements.
- Screen Readers (e.g., NVDA, JAWS): Help simulates the experience for visually impaired users.
Performing a WCAG Accessibility Test
- Automated Testing:
- Use automated tools like AXE or Lighthouse for a preliminary scan. These tools can detect common WCAG issues, such as missing alt text, color contrast issues, and improper use of HTML elements.
- Manual Testing:
- Test with screen readers and keyboard-only navigation to check the operability of interactive elements, the clarity of the page structure, and the navigation order.
- Verify multimedia content has accessible alternatives, like captions for videos.
- User Testing:
- Include users with disabilities in testing to ensure your content and design meet real accessibility needs.
Key Section 508 Success Criteria for Websites
A site passes Section 508 minimum requirements if it:
- Provides text alternatives for images, buttons, and non-text elements.
- Has captions for videos and, ideally, audio descriptions if essential visual details are present.
- Maintains color contrast ratios as per WCAG standards.
- Supports keyboard navigation for all features.
- Avoids flashing content that could cause seizures.
- Utilizes semantic HTML for assistive technology compatibility.
- Offers user feedback for form errors and necessary corrections.
- Ensures that content structure remains accessible and understandable across different devices.
- Meeting these minimum criteria aligns the website with Section 508 requirements and also ensures that it is accessible to a diverse range of users.