How it works
A system that cannot be used by part of its intended audience has failed for that audience regardless of its technical quality.
Evaluate against real constraints: screen readers, contrast, input methods, and bandwidth.
Common error
Treating accessibility as an optional final polish rather than a design constraint.
Worked example
Example
Chart distinguishes categories only by red and green
Controls require a mouse
Form errors appear without explanatory textAccessibility requires more than a visual appearance check. Add labels or patterns, keyboard-operable controls, meaningful error messages, and usable alternatives. Test with relevant users and assistive workflows.
Exercises
9.3.1 · Explain
Suggest two improvements to the chart and controls in the example.
Show solution
Add text labels or distinct patterns to categories, and make controls usable through keyboard navigation with visible focus.
9.3.2 · Explain
Why is testing only with the original developers insufficient?
Show solution
They know the intended workflow and may not represent different abilities, devices, languages, or prior experience. Broader testing reveals assumptions that developers miss.