Data Visualization Accessibility
Overview
Data presented in tables, charts, graphs, and other visualizations should be formatted so it is accessible for all users.
Key considerations for accessible data visualizations include design and color, labels and descriptions, multiple formats, and interactivity. (Source: Harvard University: Data Visualizations, Charts, and Graphs)
Design and Color
Design
- Use simple, clear designs that avoid animations.
- Do not overwhelm your audience with data. Focus on the key insights you want to communicate.
- Use appropriate font sizes and ensure the visualization can be resized.
Color
- Ensure sufficient color contrast between text, graphics, and backgrounds.
- Do not use CU gold on white (and vice-versa).
- WebAIM contrast checker (WCAG AA standard)
- Use accessible color palettes.
- Do no rely on color alone to convey meaning.
- Use labels and shapes in addition to color.
Chart Accessibility Comparison
Which chart is more accessible?
Chart 1 uses shapes to indicate the series of each line (not just the color of the line) and includes a clear legend. It also has sufficient color contrast between the lines and white background.
Imagine the charts are in grayscale; would you be able to understand Chart 2?
Labels and Descriptions
- Clearly label titles, axes, and data points.
- Use legends to distinguish data.
- Include a short description (alt text) for simple visualizations or a long description for complex visualizations.
Example alt text for pie chart: "Sales by quarter: 1st quarter 58%, 2nd quarter 23%, 3rd quarter 10%, 4th quarter 9%."
Multiple Formats
- Present data in multiple formats to support a variety of learning needs. Your audience can choose what works best for them.
- In addition to charts and graphs, share data as tables, spreadsheets, and/or text descriptions.
Interactive Data Visualizations
- Interactive data visualizations require additional accessibility considerations for keyboard-only and screen reader users. All data should be navigable using only a keyboard (no mouse) and screen reader tools should be able to read all data.
- Provide alternative formats when needed to ensure access to data.