Accessibility: Data Visualizations

Why Is This Important?

Ensuring accessible visual data allows for equal access to information, improves comprehension, reduces cognitive load and leads to better data communication.

When To Use It

When there is a visual chart, graph, map, etc., there needs to be an accessible caption or chart along with it.

How To Use It
  • Use color sparingly, and ensure adequate color contrast.
  • Provide alternative text.
  • Label everything clearly.

Data Visualization Checklist:

  1. Can someone understand this data without color?
  2. Is there enough contrast?
  3. Is there a text description?
  4. Can I tab through the data?
  5. Are labels clearly defined and direct?

Best Practices

  • The most accessible approach to visual data is to provide multiple formats so users can choose what works best for them.
  • Reduce interpretation steps through labeling lines directly, annotating peaks and embedding values into data points.
  • If a visual chart is deemed necessary, ensure that it supports the text-based chart.
Accessible Data Visualizations
Color
  • Refrain from using color alone to convey meaning.
  • Use patterns or shapes to differentiate information and make data stand out more.
Labels
  • Ensure major elements are identified, such as the title, horizontal and vertical axis, and other notable framework elements.

  • Use labels and legends that clearly mark and distinguish the data points.

    Direct Labeling Example
    Direct Labeling Example
    Data Point Callout Example
    Data Points Callout Example
Supplemental Formats
  • Presenting data in multiple formats allows users to digest information in ways that best suit their needs.

  • Supplemental formats include a hyperlink to the raw data or alternative text, providing a chart description, using figure descriptions (such as from a textbook) or even a different chart.

    Supplemental Formats Alternative
    Table Supplemental Image
Maps
  • Images of maps must have a descriptive text alternative appropriate to its content.
  • Ensure there is a description of the purpose of the map so users can interpret the data.

  • If a map application cannot be accessed using a keyboard, consider using a different application to ensure access for all.

    Accessible Map Example
    Accessible Map Example
Tips for Checking Accessibility

Testing Methods:

  • Convert your data visualization to grayscale. If you cannot interpret the data, change your visualization.
  • Hide the legend. If your chart becomes confusing, add labels directly.
  • Run a 10-second comprehension test. If users cannot understand the main point within 10 seconds, the chart is too complex.
  • Use a screen reader, and try navigating the data using solely a keyboard.
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