Format displayed data text as human-readable values

Format displayed chart text into human-readable values before release. For example, shorten a long visual number such as 6500000000 to a readable label such as 6.5b, and expose the screen-reader version as fully spoken text such as “six point five billion”; apply the same formatting to axes, data labels, annotations, tables, and legends.

Raw numeric strings and compressed terms force readers to translate the display before they can understand the data. A paired visual form and screen-reader form reduces that decoding work and makes the same value easier to interpret across visual and nonvisual reading.

Mechanism: Human-readable formatting reduces cognitive and functional labor by turning raw strings into values that can be understood directly on sight and parsed comfortably when read aloud.

Evidence: Chartability requires all displayed textual information in labels, annotations, axes, tables, and legends to be formatted to a human-readable level and to have versions that screen readers can parse comfortably, including the example of showing 6500000000 visually as 6.5b and exposing it to screen readers as “six point five billion” (Elavsky et al., 2022). The linked WCAG understanding document supports explaining unusual words, jargon, and acronyms so people with cognitive disabilities and screen-reader users can understand the content (W3C, n.d.).

Notes: This guidance applies to displayed data text broadly, not only to axis labels.

• User Goal: Read values and terms directly without mentally expanding raw strings.
• Data: Large numbers, abbreviations, acronyms, or other hard-to-parse text appear in displayed chart text.
• Chart Setting: The chart exposes text in axes, data labels, annotations, tables, legends, alt text, or other screen-reader labels.
• Audience: Includes screen-reader users and readers who benefit from more understandable wording.
• Success Criterion: The visual text and the screen-reader text can each be understood comfortably without manual translation.

Break it when: the value or term is not exposed as text at all and remains only visual. Why: reformatting text cannot help readers or screen readers if the information is missing from labels, annotations, tables, legends, or other text outputs.

Sacrifice: The visible label may show a shortened form instead of the full raw string. Risk: Visual shorthand and screen-reader wording can drift apart if they are edited separately. Mitigation: Keep the visual abbreviation and the screen-reader expansion aligned to the same underlying value.

• Mistake: Leaving raw numeric strings or unexplained abbreviations in axis labels, legends, or annotations. Why it fails: readers must reformat the text mentally before they can understand the value.
• Mistake: Reusing the same compressed visual string in screen-reader labels or alt text. Why it fails: the screen-reader version is not the comfortably parsed spoken form this guideline requires.

Failure Sign: Axis labels, data labels, table cells, legends, or annotations contain long digit runs, abbreviations, acronyms, or other strings that are hard to parse directly. Quick Check: Scan each displayed text element and ask whether a reader can understand it without expanding or decoding it mentally. Stronger Test: Inspect the screen-reader label or alt text for a large value and confirm that it expands the visual shorthand into a fully spoken form.

• Rewrite long numeric strings in visible axes, labels, tables, legends, and annotations into compact human-readable forms.
• Add screen-reader labels or alt text that expand visual shorthand into fully spoken values.
• Replace unexplained acronyms, jargon, or unusual terms with clearer wording, or add an explanation where the term must remain.
• Apply the same formatting rule consistently across all displayed text elements in the chart.