How Bionic Reading works

Bionic Reading was introduced by Swiss typographic designer Renato Casutt. The idea is to mark the beginning of each word with a bold fixation point so the reader's brain can finish the word automatically. This reduces micro-saccades (the tiny back-and-forth eye movements that slow reading) and can increase both speed and comprehension.

The saccade parameter

Saccade refers to the rapid eye movement between fixation points. In this tool the saccade slider controls what fraction of each word is bolded - from a very light highlight of just the first letter (saccade 1) up to bolding more than half the word (saccade 5).

Usage tips

Start with saccade 2 (the default) and adjust until you find your preferred density.
Copy as HTML to paste into email clients, Notion, or any rich-text editor.
Works best with body text; very short words (1–2 letters) are bolded entirely.

Scientific evidence

The scientific evidence for Bionic Reading improving reading speed or comprehension is currently limited. Independent peer-reviewed replications have produced mixed results - some studies find modest benefits for readers with ADHD or dyslexia; others find no statistically significant effect for typical readers. The trademark holder (Renato Casutt) reports improvements in internal testing, but large-scale independent trials with pre-registration are lacking as of 2025. Treat it as a personal experiment rather than a proven intervention.

Who benefits most

Anecdotal reports and small-scale studies suggest the people most likely to notice a benefit are:

Readers with ADHD: the bold anchors may help maintain attention on the current word and reduce mind-wandering during long passages.
Readers with dyslexia: the visual emphasis can help track position on the page, though dedicated dyslexia typefaces (OpenDyslexic, Lexie Readable) may provide greater benefit.
Speed readers: some experienced speed readers find the anchors reinforce the fixation habits they have already developed.