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Chart and Diagram Text Equivalents

Last updated: 4 Oct 20266 min read
tutorial
IntermediateBy AITrove Editorial

A chart compresses numbers and relationships into a visual form. A short alternative can identify what the chart is about, but it cannot carry every data point or relationship a reader may need. Provide the important result in nearby prose and give access to the underlying values or a structured explanation. The equivalent should answer the same task as the graphic: identifying a trend, comparing cases, or finding an outlier. Color, symbol position, and hover tooltips alone cannot serve as the only channel for that information. The data revision shown in text must match the rendered chart.

Working case

A case dashboard plots unresolved inspections by district across four weeks. District North rises from 23 to 47, while East falls from 42 to 31. The visual bars make the difference quick to see, but a reviewer also needs exact values and the date range. Place a concise statement of the meaningful change before the chart, then offer a text list of weekly district counts in a sensible order. A diagram of the review process needs its branch conditions and outcomes in text, not just colored arrows that disappear when the image fails.

Implementation boundary

javascript
function districtChange(firstWeek, lastWeek) {
  return { direction: lastWeek >= firstWeek ? "up" : "down", amount: Math.abs(lastWeek - firstWeek) };
}
console.log(JSON.stringify(districtChange(23, 47)));
// Output: {"direction":"up","amount":24}

Build the chart and its text equivalent from the same normalized data object and revision so they cannot silently diverge. A short image alternative identifies the visual, while visible text or a linked detail supplies the values and relationship. For interactive charts, do not rely on hover alone; keyboard users need a way to reach data points, or a text representation that supports the same question. Label units, time zone, and missing-data rules. If a chart aggregates private records, authorize the text equivalent and downloadable values under the same policy as the graphic.

Cost and boundaries

Producing a textual list of n data points is O(n) time and output space. For thousands of points, a full inline listing can overwhelm readers, so provide meaningful summary, filters, and an accessible data view with pagination or an approved export. A second manually maintained summary is cheaper to implement today but becomes inaccurate after data updates. Reusing a normalized data model costs design work and reduces drift. Test that the largest, smallest, and missing values in the text match the chart’s current revision and permissions.

Failure trace

The dashboard adds a short alternative reading bar chart but no values or trend in text. A reviewer cannot determine which district crossed an escalation threshold without seeing the bars. Add a plain-language result and data access path. Another chart uses red and green alone to encode status; monochrome viewing loses the meaning. Provide explicit labels and values. Change a filter from All districts to North and confirm the summary and text values update together. A stale text equivalent can be worse than no summary because it looks authoritative.

Verification

  • A reader can answer the chart’s core questions from text.
  • Text and visual states share the same filter and revision.
  • Protected aggregates remain protected in both presentations.

Practice drill

Start with the four-week district dataset and write three questions the chart is supposed to answer. Verify each can be answered from text alone. Remove colors, disable hover, use keyboard only, and inspect the filtered state with a screen reader. Change one underlying count and assert that the chart, result sentence, and value list use the same revision. Try an unauthorized district account and verify neither graphic nor text reveals protected counts.

Decision note

Give complex visuals a concise identity and a synchronized text path to the actual data and conclusion.

Common Mistakes

  • Using a generic chart label as the entire equivalent.
  • Encoding status only by color or hover.
  • Maintaining chart and text values in separate unsynchronized data paths.

Connected lessons

Accessible Content and Media; Image Alternatives by Purpose; Captions, Transcripts, and Media Controls; Landmarks, Headings, and Skip Paths; Data Table Versus Interactive Grid; Structured Data from Visible Facts; Search Permissions and Private Results.

Apply and check

Build Project: accessible inspection report and review Web Development: accessible content and privacy decisions quiz.

Further connections

Interactive Graphics and Canvas Boundaries; Accessible Graphic Controls and Text Equivalents.

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