Data is a cornerstone of decision-making, and charts and graphs play an essential role in how we communicate that data visually. From business reports to academic research and government statistics, visual representations of data help us understand complex information more quickly. However, for many users, such as those with visual or cognitive disabilities, charts and graphs can present significant barriers. Making these visual elements accessible is crucial to ensure that everyone, regardless of ability, can interpret and benefit from the information they contain.

In this post, we will explore the best practices for making accessible charts and graphs, so that all users can access and understand the data you’re presenting.

Why Accessibility in Charts and Graphs Matters

According to the World Health Organization, approximately 15% of the world’s population experiences some form of disability, and many of those individuals rely on digital accessibility practices to navigate the web. If your charts and graphs are inaccessible, you are excluding a significant portion of the population from understanding and using the information you present.

While web accessibility standards like the Web Content Accessibility Guidelines (WCAG) provide a framework for making websites and applications more inclusive, ensuring that charts and graphs meet these standards can be tricky. Unlike text-based content, visual elements like graphs often rely heavily on color, size, and shape to convey meaning. If these visual cues are not properly communicated in an accessible way, it can make it difficult or even impossible for some users to understand the data.

Best Practices for Accessible Charts and Graphs

Creating accessible charts and graphs doesn’t mean you have to sacrifice visual appeal or the complexity of your data. It simply requires you to take a few extra steps to ensure that your visualizations are usable by everyone. Below, we’ll go over some essential best practices for creating accessible data visualizations.

Provide Textual Descriptions

The first step in making charts and graphs accessible is providing a clear textual description of the data. Screen readers, used by individuals who are blind or visually impaired, cannot interpret visual content like graphs. To make sure the data is still accessible, provide a descriptive alternative to the graphic.

Use alternative text (alt text) for charts and graphs to provide a concise summary of the data they represent. For instance, a bar chart showing monthly sales could have alt text like, “Bar chart showing monthly sales. January had the highest sales, followed by February and March.” Note, however, that this is often not enough. The power of data visualization is that not only can it provide an at-a-glance understanding of the data, but also an ability to notice relationships, patterns, and details. This is all something that cannot be conveyed in a simple alt attribute.

For more complex charts, consider providing a detailed textual description. This could be in the form of a summary paragraph or a linked page that describes the chart’s content in more depth. You can also use the aria-describedby attribute to link the image to a more detailed description if needed.

Use High-Contrast Colors

Color is a common method of distinguishing different data sets or categories in charts and graphs. However, relying solely on color to convey meaning can be problematic for users with color blindness. About 1 in 12 men and 1 in 200 women experience some form of color blindness, which means they may not be able to differentiate between certain colors on your chart.

Choose color schemes with high contrast to make it easier for users to distinguish different elements. Tools like the Color Contrast Analyzer can help you check the contrast ratios. Also, avoid using color as the sole indicator of meaning. Instead, use additional markers like patterns, textures, or labels to differentiate between data sets. For example, instead of just using red and green for positive and negative values, consider adding a “+” or “–” sign, or use solid versus dashed lines in a line graph. Finally, make sure that your chart has enough contrast between text (labels, titles) and the background color to ensure readability for users with low vision.

Label Everything Clearly

One of the primary reasons charts and graphs are effective is because they provide a visual representation of relationships between data points. However, without clear labeling, users can be left confused about what those data points represent. Labels should clearly define what each axis, legend, and data point represents.

• Label all axes and data points clearly and ensure that the title of each axis reflects the unit of measurement (e.g., “Sales in USD,” or “Time in Days”).
• Include a clear chart title that explains what the graph is displaying (e.g., “Monthly Sales by Region”) and, if possible, include the key takeaway from the data, if it is static.
• Provide a detailed legend that explains the meaning of different colors, shapes, or patterns used in the graph. The legend should be simple, placed in an easily accessible location, and provide an example of whatever colors/ shapes/ patterns represent.
• For pie charts, make sure each segment is labeled with both a percentage and the category name.

Offer a Structured Alternative

Sometimes, a visual representation simply isn’t enough for some users to understand the data, especially if the graph is highly complex. A long paragraph of narrative text is also often insufficient for diving into the details. For more in-depth analysis, you should provide a text-based alternative, like a data table or list that describes the values in the chart. We usually recommend including a data table that lists the same information presented in the graph in a text format. For example, a bar chart showing the sales numbers for different months could have an accompanying table that lists the months and their corresponding sales values. Obviously, you’ll want to ensure the data table is accessible by using proper HTML tags (e.g., <th> for headers and <td> for data cells) and making it keyboard-navigable.

Ensure Keyboard Accessibility

Keyboard navigation is an essential component of web accessibility. Users who rely on keyboard shortcuts, either because of physical disabilities or because they prefer keyboard navigation, must be able to interact with your charts and graphs just as easily as users with a mouse. Ensure that any interactive elements within the chart (e.g., hover effects, clickable legends, or zoomable charts) are keyboard-accessible. This can be achieved by providing a tabindex attribute to make the elements focusable. Implement proper keyboard controls for interactions. For instance, users should be able to navigate through different segments of a pie chart or different bars in a bar chart using the arrow keys.

Accessible charting libraries give you a head start

If you’re working with complex charts, such as interactive line graphs or scatter plots, you may want to use an accessible chart library to make the process easier. Several JavaScript libraries are specifically designed to create accessible data visualizations that can handle accessibility issues like keyboard navigation, screen reader compatibility, and color contrast.

Some popular accessible chart libraries include:

• D3.js: A powerful JavaScript library for creating complex, data-driven visualizations that can be made fully accessible with the proper configuration. The work to create fully accessible charts with D3 can be pretty steep, but there’s just so much it can do. It can be overkill for a lot of stuff, but if your data is highly scientific, there’s nothing better in our opinion. Just be mindful that a lot of the accessibility will need to be home grown.
• Chart.js: A simple and lightweight charting library that can create a wide range of charts. It includes built-in support for accessibility features like screen reader compatibility.
• Highcharts: A charting library that includes accessibility features like support for screen readers and keyboard navigation. This is our go-to at AFixt and the one we recommend to customers. We’ve even done the work to switch customers to Highcharts. That’s how much we like it.

Use ARIA Landmarks and Roles

When embedding charts within web pages, use ARIA (Accessible Rich Internet Applications) roles and landmarks to help screen reader users navigate and interact with the content. For example, assign an appropriate role="graphics-document" to indicate that the content is a visual representation of data, and ensure any controls or legends within the chart are properly labeled with aria-label attributes.

Conclusion

Incorporating accessibility into your charts and graphs doesn’t have to be an overwhelming task. By following the best practices outlined above, you can ensure that your data visualizations are inclusive and accessible to all users, regardless of their abilities. Accessibility is about providing equal access to information and ensuring that everyone has the opportunity to engage with your content.

Remember, accessible charts and graphs don’t just benefit users with disabilities—they also improve the overall user experience, making your website more user-friendly, boosting SEO, and helping you comply with accessibility laws and guidelines. Whether you’re creating a simple bar chart or a complex scatter plot, taking the time to implement these best practices will go a long way toward making your data visualization truly inclusive.