Accessible Charts and Graphs

Accessible charts and graphs ensure data visualizations convey their information to all users through text alternatives, data tables, and proper labeling. Visual representations of data require thoughtful accessibility implementations.

What Are Accessible Charts and Graphs

Charts and graphs visualize data through shapes, colors, positions, and sizes. Bar charts, line graphs, pie charts, and scatter plots convey patterns and relationships visually. Screen reader users cannot perceive these visual representations without text alternatives.

Accessibility for data visualizations involves multiple approaches: brief text descriptions of key findings, detailed data tables providing the underlying values, proper labeling of visual elements, and potentially sonification or interactive exploration for complex datasets.

WCAG Success Criterion 1.1.1 requires text alternatives for non-text content. Charts are complex cases where multiple forms of alternative content may be needed to provide equivalent information.

How Accessible Charts and Graphs Work

Brief descriptions summarize the key message the chart conveys. A bar chart comparing quarterly sales might be described: “Bar chart showing sales increased each quarter, from $2M in Q1 to $5M in Q4.” This captures the insight without every data point.

Data tables provide complete underlying data. A table accompanying the chart lists all values precisely. This allows screen reader users to explore the data in full, applying their own analysis.

Accessible SVG charts can include descriptive title and desc elements. The title provides a brief label; desc provides more detailed explanation. Screen readers announce these when encountering the SVG.

Interactive accessibility allows keyboard navigation through data points. When users focus on a data element, screen readers announce its value and context. This enables exploration similar to what sighted users do by visual inspection.

Color should not be the only differentiator between data series. Patterns, shapes, or labels distinguish series for colorblind users. Legends need to be perceivable through means other than color alone.

Proper labeling includes axis labels, data point labels where appropriate, and clear legends. These labels should be text (not images) and associated with the visual elements they describe.

Key Considerations

• Provide brief description capturing the chart’s key message
• Include accessible data table with complete underlying values
• Use descriptive title and desc in SVG charts
• Ensure legends and labels are text-based
• Differentiate data series through more than color
• Consider keyboard navigation for interactive charts
• Test with screen readers to verify descriptions convey meaning

Common Questions

What should chart descriptions include?

Chart descriptions should communicate: what kind of chart it is, what it shows (variables and relationships), and the key insight or trend. “Line graph showing website traffic from January to December 2024, with steady growth from 10,000 to 25,000 monthly visitors.”

Do not simply say “chart of data” or describe visual appearance without meaning. Focus on what users should understand from the chart.

When are data tables required alongside charts?

Data tables should accompany charts whenever users might need precise values or want to explore the data themselves. Complex datasets benefit from tables that allow detailed exploration.

Simple charts communicating a single clear message might rely on description alone. A pie chart showing “60% desktop, 40% mobile” might not need a separate table if the description conveys this.

How can interactive chart exploration be made accessible?

Interactive charts can support keyboard navigation through data points. When focus moves to a bar, point, or segment, screen readers announce the data value and category.

ARIA attributes help: aria-label on data elements, aria-describedby for additional context, and live regions announcing changes during data exploration or filtering.

Summary

Accessible charts and graphs combine brief descriptions of key insights, detailed data tables providing complete values, proper SVG labeling, and potentially interactive keyboard navigation. Multiple accessibility approaches ensure users with different needs can access visualized information.