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 (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 (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.