What TanStack Charts does for pie and donut 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 slice. 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 slice.
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. "Visitors by browser, June" works. "Pie chart" 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="Visitors by browser, June"
ariaDescription="Chrome brings 30% of visitors, more than any other browser."
/>
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
Label every slice with its name and percentage, beside the slice or inside it, so no one has to match colors to a legend.
Separate the slices with a thin line in the background color, using stroke and chartColors.surface, so neighbors with close colors stay apart.
To point at one slice, pull it out with a larger outerRadius, not only a brighter fill.
Marks need enough contrast with the background. Check light colors from a palette against the page in light and dark mode.
Say the percentage
A screen reader user hears the tooltip, not the angle. Put the slice's share in the tooltip next to its value, such as "Chrome, 275 visitors, 30%". The fraction field that pie adds to every row holds that share.
Small slices need a table
A thin slice is hard to hit with a pointer and too narrow for a label. Group the smallest slices into Other, and give the full list in a table under the chart, so every value is reachable without aiming at a sliver.
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 slice 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.