Bionic Reading Converter
Bionic reading bolds the first part of every word. The claim is that the eye can complete the rest, so reading becomes faster.
The bionic reading converter bolds the first portion of every word, with the fixation strength adjustable from 20 to 80 percent. The technique is popular and the evidence for it is weak, the two independent studies that have tested reading speed found no improvement, and the page says so rather than repeating the marketing claim.
How it works
For each word, the number of letters to bold is the letter count multiplied by the fixation ratio, rounded, with a minimum of one. Punctuation is not counted as a letter but stays attached to the word.
bolded letters = max(1, round(letter count x ratio))
- ratio
- the fixation strength, 0.2 to 0.8
- max(1, ...)
- guarantees at least one bolded letter, so short words are still marked
The output copies as Markdown with double asterisks, since plain text has no bold and pasting styled HTML into most editors loses the formatting anyway.
Examples
Default fixation
Text
Reading becomes faster
Fixation
50%
Result
**Read**ing **beco**mes **fas**ter
Seven letters in "reading" gives 3.5, rounded to 4. Six in "faster" gives 3. The rounding is why word lengths do not map to a constant proportion.
Short words at low fixation
Text
a of the
Fixation
20%
Result
**a** **o**f **t**he
20 percent of one letter rounds to zero, so the minimum of one applies. Without it, short function words would lose their marker entirely and the text would look inconsistent.
Limits worth knowing
Bionic Reading is a trademark of Bionic Reading AG. This tool implements the general fixation-bolding technique and is not affiliated with, endorsed by or derived from their product.
Frequently asked questions
Does bionic reading actually make you read faster?
The published evidence says no. A 2022 study by Rajaraman and colleagues and independent testing by readability researchers both found no significant improvement in reading speed or comprehension, and some participants read more slowly. The technique may still suit you personally. It just does not have the general effect its marketing claims.
What does the fixation strength actually change?
The proportion of each word that gets bolded. At 20 percent only the first letter or two are marked; at 80 percent most of the word is, which largely defeats the purpose since the contrast between bold and plain disappears.
Why does the output copy as Markdown rather than formatted text?
Because plain text has no bold, and copying HTML loses its formatting in most destinations anyway. Markdown asterisks survive the paste and render correctly anywhere Markdown is supported.
Is it useful for dyslexia?
There is no good evidence that it is, and the British Dyslexia Association’s guidance focuses on font choice, spacing and line length instead, all of which have supporting research. Treat any claim that bionic reading helps dyslexic readers as unproven.