A static chart can be one image: role="img" on the <svg>, labeled by a title and a summary sentence. An explorable chart exposes its marks as a role="list" of role="listitem" bars whose aria-label states the data in words. Saved as booknest-a11y.js:
function accessibleRatings(svg, ratings) {
const rows = ratings.map(r => ({ ...r.book, n: d3.sum(r.counts),
mean: d3.sum(r.counts, (c, i) => c * (i + 1)) / d3.sum(r.counts) }))
.sort((a, b) => b.mean - a.mean);
const y = d3.scaleBand(rows.map(r => r.title), [0, 150]).padding(0.2);
const x = d3.scaleLinear([0, 5], [170, 470]);
svg.attr('role', 'group').attr('aria-labelledby', 'chart-title chart-summary');
const bars = svg.append('g').attr('role', 'list').attr('aria-label', 'Books by mean rating')
.selectAll('g').data(rows).join('g').attr('role', 'listitem')
.attr('aria-label', r => `${r.title}: ${r.mean.toFixed(2)} stars from ${r.n} reviews`)
.attr('transform', r => `translate(0,${y(r.title)})`);
bars.append('rect').attr('x', x(0)).attr('width', r => x(r.mean) - x(0))
.attr('height', y.bandwidth()).attr('fill', r => r.color);
bars.append('text').attr('x', x(0) - 6).attr('y', y.bandwidth() / 2).attr('dy', '0.35em')
.attr('text-anchor', 'end').attr('aria-hidden', 'true').text(r => r.title);
return bars;
}The page supplies chart-title and chart-summary; visible titles are aria-hidden since labels repeat them. Chrome 1 's accessibility tree (read over the DevTools Protocol) shows a named group with a list of six named items. A data table behind a "Show data" button is the most robust fallback.
<!doctype html>
<style>
body { margin: 0; padding: 8px; background: #fafaf7; font: 12px system-ui, sans-serif; color: #263238; max-width: 600px; }
h3 { font-size: 14px; margin: 0; }
#chart-summary { margin: 2px 0 6px; }
svg { width: 100%; display: block; }
ol { margin: 6px 0 0; padding-left: 20px; font-size: 11px; color: #546e7a; }
table { border-collapse: collapse; margin-top: 6px; }
td, th { border: 1px solid #ddd; padding: 2px 6px; }
</style>
<script src="https://cdn.jsdelivr.net/npm/d3@7.9.0/dist/d3.min.js"></script>
<h3 id="chart-title">Mean star rating per book</h3>
<p id="chart-summary">Salt and Saffron rates highest (4.81); Small Steps to Big Summits lowest, from only 65 reviews.</p>
<svg viewBox="0 0 520 150" font-size="12"></svg>
<p><button id="show" aria-expanded="false">Show data</button> What a screen reader hears:</p>
<ol id="spoken"></ol>
<div id="table" hidden></div>
<script>
// BookNest sample data, invented for these examples (not real sales)
const SALES = (() => {
const books = [
{ id: 1, key: 'harbor', title: 'The Quiet Harbor', author: 'Elena Marsh', genre: 'Fiction', color: '#1f5f8b', price: 18.99, rating: 4.6 },
{ id: 2, key: 'deepweb', title: 'Patterns of the Deep Web', author: 'Ravi Menon', genre: 'Technology', color: '#5b3f99', price: 39.5, rating: 4.3 },
{ id: 3, key: 'saffron', title: 'Salt and Saffron', author: 'Leila Haddad', genre: 'Cooking', color: '#e09a10', price: 24, rating: 4.8 },
{ id: 4, key: 'summit', title: 'Small Steps to Big Summits', author: 'Tom Okafor', genre: 'Self-Help', color: '#3f7d3a', price: 14.99, rating: 4.1 },
{ id: 5, key: 'clock', title: "The Clockmaker's Paradox", author: 'Iris Vale', genre: 'Science Fiction', color: '#b5452f', price: 16.2, rating: 4.5 },
{ id: 6, key: 'glass', title: 'Gardens in Glass', author: 'June Park', genre: 'Gardening', color: '#2a9d8f', price: 22.5, rating: 4.4 },
];
const units = { // units sold per month, January 2025 to August 2026
1: [40, 47, 46, 47, 57, 51, 46, 54, 60, 60, 71, 111, 52, 42, 49, 56, 59, 48, 53, 51],
2: [40, 37, 35, 41, 48, 43, 40, 42, 50, 53, 53, 84, 42, 35, 38, 41, 45, 41, 46, 46],
3: [46, 45, 41, 46, 53, 49, 46, 45, 60, 51, 63, 100, 48, 48, 49, 48, 53, 49, 48, 52],
4: [100, 80, 72, 70, 66, 66], // released March 2026
5: [48, 47, 54, 52, 65, 55, 57, 58, 64, 66, 75, 124, 58, 49, 59, 56, 63, 57, 54, 57],
6: [31, 30, 28, 35, 31, 32, 29, 30, 41, 36, 45, 64, 31, 30, 30, 38, 40, 38, 36, 38],
};
const months = d3.utcMonths(new Date('2025-01-01'), new Date('2026-09-01')).map(d3.utcFormat('%Y-%m'));
const sales = books.flatMap(b => units[b.id].map((n, i) =>
({ month: months[i + months.length - units[b.id].length], book: b.id, units: n })));
const ratings = [[4, 8, 20, 87, 293], [6, 10, 22, 95, 147], [2, 3, 8, 45, 342], [2, 3, 8, 24, 28],
[4, 8, 20, 90, 228], [4, 7, 20, 82, 147]].map((counts, i) => ({ book: i + 1, counts })); // 1 to 5 stars
const regions = [{ id: '826', name: 'United Kingdom', units: 1480 }, { id: '276', name: 'Germany', units: 1120 },
{ id: '250', name: 'France', units: 760 }, { id: '372', name: 'Ireland', units: 540 },
{ id: '528', name: 'Netherlands', units: 410 }, { id: '724', name: 'Spain', units: 320 }];
const links = [[5, 1, 38], [1, 3, 24], [2, 5, 18], [3, 6, 21], [4, 1, 12], [2, 6, 9], [4, 3, 15], [5, 6, 14]]
.map(([source, target, value]) => ({ source, target, value })); // customers who bought both
return { books, sales, ratings, regions, links };
})();
// prepareSales(raw): parsed dates, sales linked to book objects, revenue and totals
function prepareSales(raw) {
const parse = d3.utcParse('%Y-%m'), books = raw.books.map(b => ({ ...b }));
const byId = d3.index(books, b => b.id);
const sales = raw.sales.map(s => ({ date: parse(s.month), book: byId.get(s.book),
units: s.units, revenue: s.units * byId.get(s.book).price }));
for (const [book, rows] of d3.group(sales, s => s.book)) {
book.units = d3.sum(rows, s => s.units);
book.revenue = d3.sum(rows, s => s.revenue);
}
const months = d3.rollups(sales, v => ({ units: d3.sum(v, s => s.units),
revenue: d3.sum(v, s => s.revenue) }), s => +s.date).map(([t, v]) => ({ date: new Date(t), ...v }))
.sort((a, b) => a.date - b.date);
const ratings = raw.ratings.map(r => ({ ...r, book: byId.get(r.book) }));
return { ...raw, books, sales, months, ratings };
}
function accessibleRatings(svg, ratings) {
const rows = ratings.map(r => ({ ...r.book, n: d3.sum(r.counts),
mean: d3.sum(r.counts, (c, i) => c * (i + 1)) / d3.sum(r.counts) })).sort((a, b) => b.mean - a.mean);
const y = d3.scaleBand(rows.map(r => r.title), [0, 150]).padding(0.2);
const x = d3.scaleLinear([0, 5], [170, 470]);
svg.attr('role', 'group').attr('aria-labelledby', 'chart-title chart-summary'); // a named group
const bars = svg.append('g').attr('role', 'list').attr('aria-label', 'Books by mean rating')
.selectAll('g').data(rows).join('g').attr('role', 'listitem')
.attr('aria-label', r => `${r.title}: ${r.mean.toFixed(2)} stars from ${r.n} reviews`)
.attr('transform', r => `translate(0,${y(r.title)})`);
bars.append('rect').attr('x', x(0)).attr('width', r => x(r.mean) - x(0)).attr('height', y.bandwidth()).attr('fill', r => r.color);
bars.append('text').attr('x', x(0) - 6).attr('y', y.bandwidth() / 2).attr('dy', '0.35em')
.attr('text-anchor', 'end').attr('aria-hidden', 'true').text(r => r.title); // the label already says it
bars.append('text').attr('x', r => x(r.mean) + 4).attr('y', y.bandwidth() / 2).attr('dy', '0.35em')
.attr('aria-hidden', 'true').text(r => r.mean.toFixed(2));
return bars;
}
const bars = accessibleRatings(d3.select('svg'), prepareSales(SALES).ratings);
// Read the accessible names back out of the DOM, as assistive technology would
const svg = d3.select('svg');
const name = svg.attr('aria-labelledby').split(' ').map(id => document.getElementById(id).textContent).join(' ');
d3.select('#spoken').selectAll('li').data([`group, "${name}"`, 'list, "Books by mean rating", 6 items',
...bars.nodes().map(n => `listitem, "${n.getAttribute('aria-label')}"`)]).join('li').text(d => d);
// The most robust fallback: the same numbers as a table
d3.select('#table').html('<table><tr><th>Book</th><th>Mean</th><th>Reviews</th></tr>' +
bars.data().map(r => `<tr><td>${r.title}</td><td>${r.mean.toFixed(2)}</td><td>${r.n}</td></tr>`).join('') + '</table>');
d3.select('#show').on('click', function () {
const open = this.getAttribute('aria-expanded') === 'false';
this.setAttribute('aria-expanded', open);
d3.select('#table').property('hidden', !open);
});
</script>