Glossary
Readability
What is readability?
Readability is the ease with which text can be read and understood, determined by factors including vocabulary complexity, sentence length, typography, line length, spacing, and contrast.
How it works
Linguistic readability concerns vocabulary and sentence structure. Visual readability concerns how text is presented. Both depend on the reader’s knowledge and needs. Formulas such as Flesch-Kincaid use features such as sentence length and syllable count to estimate reading difficulty; they do not directly test comprehension. Font size, spacing, line length, contrast and user control all affect visual readability.
Applied example
Consider a hypothetical benefits-form instruction:
- Before: “Applicants are required to provide documentary verification of residency prior to submission.”
- After: “Before you submit the form, attach a document that shows where you live.”
The revision states who must act, what to do and when. A real form would also need to identify which documents it accepts; a shorter sentence or a better readability score cannot supply missing information.
A separate visual change could let readers increase line spacing or enlarge text without losing access to the form’s labels and controls. This addresses presentation rather than the meaning of the instruction. Test the wording by asking intended users what they must submit. Test the layout by checking whether they can read and use the form at their chosen settings. To estimate each change’s contribution, compare wording and layout changes separately as well as together.
Why it matters
Readable text helps people understand and use information. Test comprehension with the intended audience and allow users to adjust presentation where needed.
For example, W3C’s visual presentation criterion sets out Level AAA accessibility requirements.