Define and conquer

Let’s start by defining readability. According to a classic paper by Edgar Dale and Jeanne Chall, readability is “…the sum total (…) of all those elements within a given piece of printed material that affect the success a group of readers have with it. The success is the extent to which they understand it, read it at an optimal speed, and find it interesting.”

In other words, readability is a metric that evaluates the ease and comfort of reading a particular text.

The question of how to create this kind of metric was asked long before the web emerged—as early as the 19th century. French psychologist Louis Émile Javal provided one of the first known studies of the matter in 1879 with his paper Essai sur la physiologie de la lecture (On the Physiology of Reading).

Javal’s key insight was that readers’ eyes don’t move steadily across the text; they actually make short, rapid movements (saccades), mixed with longer stops (fixations). Javal also noted that sometimes, while reading, the eyes unconsciously move backwards to text the reader has already seen. His idea was that the number of stops and backwards moves might help determine readability level—however, Javal lacked precise tools for the task and the idea was dropped at that time.

Two other prominent approaches came forward later, in the middle of the 20th century.

One was based on the speed of perception, while another emphasized measuring overall eye fatigue. These were pioneered by two researchers, Miles Tinker and Matthew Luckiesh—whose different approaches to measuring readability even led to a certain animosity for each other (you can learn more from a paper by William Berkson).

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Consider the needs of your audience when selecting the type size: smaller type is harder to read for seniors, children and visually impaired people. Set in Spectral