*This article is an English translation of a Japanese article.
To achieve web accessibility, websites need to comply with various standards and guidelines. Among these, the Web Content Accessibility Guidelines (WCAG) are the international standard for evaluating web content accessibility. WCAG defines three compliance levels: A, AA, and AAA, with A and AA being the most common targets for web development projects. This article explains the differences between Level A and Level AA in detail.
What Are Compliance Levels?
Compliance levels indicate how well a website meets accessibility standards. WCAG defines three levels of compliance:
- Level A: The minimum accessibility level, which includes essential criteria for making web content accessible to users with disabilities.
- Level AA: A more comprehensive level, covering a broader range of accessibility needs and making the website more usable for the general public. It is the recommended level for most organizations.
- Level AAA: The highest level of accessibility, ensuring optimal access for all users. However, it is difficult to achieve Level AAA for all content.
Overview of Level A
Level A compliance ensures that a website meets the minimum accessibility requirements, removing basic barriers that prevent users with disabilities from accessing content. A website that complies with Level A typically meets the following criteria:
Key Requirements
- Provide alternative text for images: Alt text should be used to describe images for users who cannot see them.
- Support keyboard navigation: All functionality should be operable using only the keyboard.
- Present information in multiple forms: Visual information should be available in auditory formats, and auditory information in visual formats (e.g., providing captions for audio content).
- Control over autoplay: Audio or video content that plays automatically must have an option to stop or control it.
Limitations of Level A
While Level A removes fundamental barriers, it may not be sufficient for users with severe visual impairments, color blindness, or hearing disabilities. For example, low contrast or insufficient support for dynamic content may still pose challenges. Therefore, aiming for a higher compliance level is recommended.
Overview of Level AA
Level AA is the most widely adopted target level under WCAG and is often the goal for many organizations when building websites. In addition to the Level A requirements, Level AA addresses broader needs to enhance usability for a wider range of users with disabilities.
Key Requirements
- Sufficient contrast ratio: The contrast ratio between text and background should be at least 4.5:1, making the content easier to read for users with visual impairments or color blindness.
- Responsive design: Content should display correctly on various devices and maintain functionality even when zoomed in.
- Proper use of headings and labels: Headings and labels should clearly define sections of the page, making navigation easier.
- Error identification and correction: Users should be notified of input errors and provided with instructions for correction.
- Control over dynamic content: Automatically moving or changing content must have controls to allow users to pause or stop it.
Benefits of Level AA
Achieving Level AA compliance makes the website more accessible to a larger number of users with disabilities. It is also a widely recommended standard in legal requirements and industry guidelines, making it a common target for organizations aiming to ensure accessibility.
Key Differences Between Level A and AA
The main differences between Level A and Level AA are the scope and depth of the accessibility requirements.
- Wider Coverage: Level AA includes additional requirements that address the needs of more users with disabilities, such as improved visual contrast and support for correcting input errors.
- Improved Usability: Level AA compliance significantly improves the user experience for all users, potentially reducing bounce rates and increasing user engagement.
- Legal Compliance: In many regions, public institutions and certain businesses are required to meet Level AA compliance, reducing legal risks by adhering to accessibility regulations.
Conclusion
WCAG Levels A and AA each have distinct requirements and objectives. While Level A provides the minimum necessary accessibility, Level AA is the recommended target for creating a more inclusive and user-friendly website. By aiming for Level AA compliance, organizations can improve user experience, enhance legal compliance, and create a website that is accessible to a broader audience. When working to improve web accessibility, start by aiming for Level AA and, if possible, consider striving for Level AAA as part of continuous improvement.
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