Write chart text and alternative text at grade 9 or lower

Write every visible chart text element and every alternative text element to a ninth-grade reading level or lower. For example, shorten complex sentences, replace jargon with simpler wording, and if a technical term must remain, add a short plain-language explanation written at grade 9 or lower.

Lower-complexity wording reduces ambiguity and cognitive load in the text that people use to understand a visualization. Defining unavoidable specialized terms lets readers keep needed precision without making the chart text harder to process.

Mechanism: Simpler wording makes chart text easier to read directly, and plain-language explanations prevent unfamiliar terms from blocking understanding.

Evidence: Chartability marks inappropriate reading level as a critical understandable accessibility issue and requires all text and alternative text to target a reading grade level of 9 or lower, with analytical tools used to estimate readability (https://doi.org/10.1111/cgf.14522">Elavsky et al., 2022). W3C guidance says complex or unfamiliar terms should be supported with definitions or supplementary explanation, and the Hemingway Editor is described as a tool that flags complex sentences and estimates readability grade level (https://www.w3.org/TR/UNDERSTANDING-WCAG20/meaning-supplements.html">W3C, n.d.; Hemingway Editor, n.d.).

Notes: This rule applies to both visible text and alternative text.

• User Goal: Understand the visualization’s text support without extra interpretation.
• Chart Setting: The visualization includes visible text or alternative text that explains, supplements, or accompanies the data.
• Audience: Readers include people with cognitive disabilities or readers who may not know specialized terms.
• Success Criterion: Each text block reads at grade 9 or lower, and any required technical term is explained in simpler language.

Break it when: A specialized term is required for accuracy and cannot be removed. Why: The term may stay, but it must be explained with supplementary text written at grade 9 or lower.

Sacrifice: You may need extra explanatory text when a required technical term cannot be replaced. Risk: Simplifying blindly can remove terminology that is necessary for accuracy. Mitigation: Keep the required term and add a short plain-language definition beside it or in supplementary text.

• Mistake: Simplify only visible text and leave alternative text dense or jargon-heavy. Why it fails: The requirement covers all provided text, including alternative text.
• Mistake: Leave complex terminology unexplained. Why it fails: Complex terms are only acceptable when they are explained in simpler language.

Failure Sign: A readability tool scores any chart text or alternative text above grade 9, or the text contains unexplained specialized terms. Quick Check: Run a reading-level tool on every visible text block and every alternative text block. Stronger Test: Verify that each unavoidable technical term has a plain-language explanation written at grade 9 or lower.

• Rewrite long or complex sentences in visible text and alternative text until they read at grade 9 or lower.
• Replace jargon with simpler words where accuracy allows.
• Add a short plain-language definition for any technical term that must remain.