Accessibility Testing: Automated Tools and Manual Techniques

Introduction to Accessibility Testing

Digital accessibility (a11y) is the practice of designing and building websites, applications, and digital tools so they can be used by the widest possible range of people—including people with different types of disabilities. Accessibility testing is a key part of this process, helping us verify whether our digital products meet relevant standards such as the Web Content Accessibility Guidelines (WCAG).

Effective accessibility testing is based on combining two main approaches: using automated tools and applying manual techniques.

Automated Tools for Accessibility Testing

Automated tools are programs or browser plugins that scan a website’s code in search of potential accessibility issues. They’re extremely helpful for quickly detecting certain types of errors.

Advantages of Automated Tools:

• Speed: They can scan many pages in a short time.
• Repeatability: They provide consistent results in every test.
• Detecting “easy” issues: They effectively identify problems such as missing alt attributes for images, low color contrast (though not always perfectly), or mistakes in heading structure.
• Integration with the development process: Many tools can be integrated with CI/CD systems.

Limitations of Automated Tools:

• They don’t catch everything: Automated tools are estimated to detect only about 30–50% of all potential accessibility issues.
• Lack of contextual understanding: They can’t judge whether an image’s alternative text is truly meaningful, whether the order of elements makes sense to the user, or whether interactions are intuitive.
• They may generate false alarms (false positives) or miss issues (false negatives).

Examples of Popular Automated Tools:

• Lighthouse (Google): Integrated with Chrome developer tools; it evaluates accessibility, among other things.
• axe DevTools (Deque): A popular browser extension and integration library.
• WAVE (WebAIM): A plugin and an online tool for visualizing accessibility issues.
• ARC Toolkit (TPGi): A Chrome extension supporting WCAG testing.

Remember: the results from automated tools are only the beginning. They’re a great starting point for deeper, more detailed analysis.

Manual Accessibility Testing Techniques

Manual testing is essential for assessing accessibility aspects that automated tools can’t verify. It involves interacting with a website or application in the way people using assistive technologies—or with specific needs—would.

Key Manual Techniques:

• Keyboard-only navigation:

  Check whether you can reach all interactive elements (links, buttons, form fields) and activate them using only the keyboard (mainly Tab, Shift+Tab, Enter, Space, Esc, and arrow keys). Pay attention to focus visibility (the outline of the active element) and the logical order of navigation.

• Screen reader testing:

  Use popular screen readers (e.g., NVDA for Windows, VoiceOver for macOS/iOS, TalkBack for Android) to understand how content and functionality are presented to blind users. Check whether:

  • Images have meaningful alternative descriptions.
  • Form elements are properly labeled.
  • Heading structure is logical and supports navigation.
  • Dynamic content changes are communicated to the user.
  • Links make sense in context (not just “click here”).

• Page zoom (Zoom) and text resizing:

  Check whether the page stays readable and functional when zoomed to at least 200% and when you change the default font size in the browser. Content shouldn’t overlap or disappear.

• Checking color contrast:

  Although automated tools can help, it’s worth manually verifying the contrast between text and background—especially for graphic elements and text on images. Use tools like a “color picker” and contrast calculators.

• Reviewing HTML structure and semantics:

  Make sure the HTML code is used according to its intended purpose.

• Form verification:

  Check whether all form fields have associated labels (), whether error messages are clear and accessible, and whether instructions are understandable.

• Checking ARIA usage:

  If ARIA attributes (Accessible Rich Internet Applications) are used, verify that they’re implemented correctly and truly improve accessibility—not make it worse.

Bringing It Together: Automation and Manual Testing

The best results in accessibility testing are achieved by strategically combining automated tools and manual techniques. A recommended workflow is:

1. Start with automated tests: Quickly identify core issues and areas that need attention.
2. Run thorough manual tests: Focus on aspects that automation doesn’t cover, such as user experience, navigation logic, or content clarity for people using assistive technologies.
3. Test regularly: Include accessibility testing in your development cycle—not as a one-time task at the end of a project.

Summary

Accessibility testing is an essential part of creating inclusive digital products. Using both automated tools and carefully conducted manual tests allows you to detect a wide range of issues and ensure that your website or application is usable by everyone, regardless of their abilities or limitations.

Remember: accessibility isn’t only about meeting guidelines—it’s primarily about creating better experiences for every user.