What TanStack Charts does for distribution charts on its own, and what you add so that everyone can read them.
What you get
A named chart. ariaLabel is required, and the chart is exposed as an image with that name. ariaDescription adds a longer description.
Keyboard navigation, on by default. Tab moves into the chart and focuses the first bin or box. Arrow keys move between them, and Home and End jump to the first and the last. Enter or Space pins a sticky tooltip, and Escape closes it.
The tooltip is announced to screen readers as it changes, so a keyboard user hears the values of the focused bin or box.
A visible focus ring in the theme's focus color, shown for keyboard focus only.
Reduced motion. Animated charts skip their animation when the reader has asked for less motion.
An interactive legend made of real buttons, each with a pressed state, when you use interactiveColorLegend.
What you add
A label that says what the chart shows, its unit and its period. "Number of cars by fuel economy, in steps of 5 mpg" works. "Histogram" does not.
A visible title, and a subtitle with the unit and the period, in HTML next to the chart.
The exact values another way, when they matter: a table under the chart, behind a toggle, or a download.
A second signal besides color for every series or part.
A keyboard path for every control you add yourself, such as a series filter or a period picker.
Name and describe the chart
Keep the label short and put the takeaway in the description. Do not put every value into the name: a screen reader reads it in one breath.
<Chart
definition={definition}
ariaLabel="Number of cars by fuel economy, in steps of 5 mpg"
ariaDescription="Most cars get 15 to 25 mpg, and few get more than 35."
/>
Give the values as a table
A table is the most reliable way to give exact values to everyone, including people who zoom far in or print the page. Render the same array the chart reads with the kit's Table, under the chart or behind a "Show as table" switch. When the values are only an illustration, a one sentence summary is enough.
Do not rely on color
Compare groups side by side, or in one panel each, instead of overlapping them in different colors.
Write the group name on the axis or next to each box, violin or ridge, so the legend is not the only key.
Give the median line a strong color or a heavier stroke, so it stands out from the box in grayscale.
Marks need enough contrast with the background. Check light colors from a palette against the page in light and dark mode.
Say what the shape shows
A screen reader user who steps through bins hears counts, not a shape. Put the shape into words in ariaDescription or a sentence next to the chart.
Where most values sit, and the median.
Whether the shape is skewed, or has two peaks.
The outliers that matter, and how many values there are.
Explain the summary
Not every reader knows what a box, a whisker or an error bar stands for. Say it in the subtitle or the tooltip, such as "Box: middle half of the values. Line: median." Put the sample size of each group in the tooltip and in any table.
Turning the keyboard off
A static chart with no tooltip can pass keyboard: false in the second argument of defineChart, so it does not add a tab stop. Keep it on for any chart that shows values on hover: otherwise keyboard users never see them.
Check it
Tab into the chart and read every bin or box with the arrow keys.
Listen to it with a screen reader.
Zoom the page to 400% and confirm the values are still there.
View it in grayscale and confirm the series are still apart.
The Accessibility guideline has the principles that apply to every chart.