Blog · Comparisons
Bionic Reading vs OpenDyslexic
On paper they sound like rivals — two techniques that promise to make reading easier. In practice they don't really compete. Bionic Reading changes how words are rendered; OpenDyslexic changes what the letters look like. They target different problems, the evidence behind them is very different, and choosing between them mostly comes down to knowing which problem you actually have.
The short answer
If you have dyslexia and the issue is letter confusion or rotation (b/d/p/q flipping), try OpenDyslexic first. The research is modest but consistent on subjective ease-of-reading.
If you don't have dyslexia but want to read faster and reduce regressions, Bionic Reading is worth a five-minute trial. The independent evidence is weaker than the marketing suggests, but it's free to test and some readers genuinely like it. If you're a dyslexic reader hoping Bionic Reading will fix your reading, the honest answer is: it probably won't, and it may actively slow you down.
What they actually do
Bionic Reading: bolded fixation points
Bionic Reading, created by Swiss designer Renato Casutt and released in 2022, is a rendering technique. It takes any text and automatically bolds the opening portion of each word — typically the first one to three letters, scaled to the word's length. The underlying hypothesis is that your eye needs to land only on those "fixation points" to recognise a word, and the bolded fragment acts as a visual anchor that pulls the eye forward:
The technique exploits a real phenomenon. Reading is not letter-by-letter; it's a series of rapid eye jumps (saccades) that land at fixation points several characters into each word, plus periodic regressions where the eye flicks back to re-parse something. Casutt's claim is that bolding the fixation point gives the eye a strong attractor, so it needs fewer regressions and can move forward faster.
OpenDyslexic: weighted letter shapes
OpenDyslexic is a typeface, not a rendering trick. Released in 2011 by Abelardo Gonzalez and maintained as open source, it redraws every glyph so that the bottom of each letter is visibly heavier than the top. The lowercase b, d, p and q — which many dyslexic readers report mistakenly rotating or flipping in their perception — each have a distinct asymmetric weight that anchors them in space:
Where Bionic Reading changes the presentation of text you could read in any font, OpenDyslexic changes the font itself. You can actually combine them — apply OpenDyslexic, then run Bionic Reading on top — and the two techniques don't conflict. They're just not solving the same problem.
Side-by-side
| Bionic Reading | OpenDyslexic | |
|---|---|---|
| What it changes | The rendering (bolding leading letters) | The typeface itself (weighted-bottom letter shapes) |
| Problem it targets | Slow reading, excessive regressions, attention drift | Letter confusion, b/d/p/q rotation, visual ambiguity |
| Audience | General readers, ADHD, light cognitive load | Dyslexic readers specifically |
| Cost | Free on many apps; paid API for commercial use | Free (SIL Open Font License) |
| Evidence base | Weak — no peer-reviewed study has replicated the speed claims | Mixed — modest objective gains, strong subjective preference |
| Works in the browser | Yes, via extensions or reader-mode apps | Yes, via LexiFont or other font-override tools |
What the research actually says
Bionic Reading
The marketing around Bionic Reading is more assertive than the evidence supports. The company's own materials reference internal studies showing improvements in reading speed and comprehension, but those studies have not been independently replicated, peer-reviewed, or published with raw data.
Independent work has been unkind to the technique. A 2022 study out of the University of Michigan, widely covered at the time, found no significant improvement in reading speed and a small but statistically significant drop in comprehension for readers using Bionic Reading versus plain text. Cloudflare, which briefly experimented with Bionic Reading on their blog, ran an informal A/B test and reported that readers using the bionic version spent roughly the same time on the page but engaged slightly less with the content.
The most charitable reading of the current evidence: Bionic Reading probably doesn't make you read faster, and it may slightly hurt comprehension on long-form text. That said, some readers — particularly those with ADHD or attention difficulties — report that the bolded anchors help them stay on the line and reduce drift. That's a real benefit even if speed doesn't improve. See our full write-up on reading tools for ADHD for more on this.
OpenDyslexic
The research on OpenDyslexic is, ironically, stronger than the research on Bionic Reading despite being nearly a decade older. Studies by Rello and Baeza-Yates (2013) and Wery and Diliberto (2017) tested OpenDyslexic against Arial and Times New Roman in school-age dyslexic populations. Objective reading speed and accuracy were roughly unchanged — but subjective preference for OpenDyslexic was consistently high, and error rates on specific letter-confusion tasks dropped.
That pattern — no speed gain, but fewer errors and higher comfort — is worth more than it sounds. Reading comfort is the main driver of how much you read, and reading volume compounds. A font that doesn't speed up your reading but makes you willing to read another article is doing real work. See our deeper dive on OpenDyslexic in Chrome for the full picture.
Which one is for you?
The tells are pretty clear:
Try Bionic Reading first if …
- You catch yourself re-reading the same sentence two or three times on long articles.
- You have ADHD or find your eye wandering off the line.
- You don't have dyslexia — you just want to plough through a long read faster.
- You're reading in a language you know well. (Bionic Reading is strictly worse in a language you're still learning: the bolded fragments don't map to meaningful morphemes, and your brain has to do extra work ignoring them.)
Try OpenDyslexic first if …
- You have a dyslexia diagnosis, especially if letter rotation (b/d, p/q, m/w) is part of your experience.
- You find that certain letterforms "swap" or "dance" on the page.
- You've already tried reader mode and font-size tweaks and still find reading effortful in a way that feels like the shapes themselves are the problem.
- You want to see if a font alone can make a difference before committing to any rendering plug-in.
The case against each
Bionic Reading's weakness is that the underlying mechanism doesn't quite hold up. The fixation-point theory is real but oversimplified: fixation points are not always at the start of a word, they shift with word length, morphology, and predictability, and manually bolding the first few letters often misaligns with where your eye would naturally land. There's also a fatigue factor: reading densely bolded text for more than a few hundred words tires most readers faster than reading plain text. Plenty of people love it for short, bursty content (articles, emails) and find it actively irritating for books.
OpenDyslexic's weakness is that the weighted-bottom hypothesis has never been proven to reduce reading time. It does seem to reduce letter-confusion errors for some readers. But the typeface itself is visually noisy — the heavy bottoms make the text feel bouncy, and it's an ugly default for most body copy. If you don't have the specific letter-rotation issue it targets, you're bearing the aesthetic cost without getting the benefit.
Can I use both?
Yes. Nothing about Bionic Reading conflicts with OpenDyslexic — the bolding operation happens at the rendering layer, the font choice at the typeface layer. You can set OpenDyslexic as your reading font and then apply a Bionic Reading plug-in on top. Some readers find this combination useful. Others find it visually overwhelming: both techniques add visual weight to the page, and doing both at once can crowd the text.
The honest recommendation is to try each one alone for a day before stacking them. If you stack, start with OpenDyslexic and add Bionic Reading only on articles where you feel your attention drifting.
How to test each one right now
Neither technique requires commitment. You can A/B them on the same article in under a minute.
To try OpenDyslexic: install LexiFont. The free tier applies OpenDyslexic to every website with one click. Read something long-form — a Wikipedia article, a news feature, a blog post — for five minutes. You usually know by the second paragraph whether the shapes are helping or hindering.
To try Bionic Reading: any reader-mode app with "bionic" or "focus" mode (Readwise Reader, Matter, and several Chrome extensions implement the technique under various names, sometimes licensed from Bionic Reading AG and sometimes using the open-source equivalent). Read the same article you just read in OpenDyslexic. Note whether your eye moves faster, slower, or the same.
The pragmatic test: after five minutes in each technique, ask yourself whether you want to keep reading. That's the real metric. Speed gains of 5% don't matter if the technique makes you close the tab; a slower but more comfortable read compounds into more reading overall.
Get LexiFont Pro — OpenDyslexic, Lexend, Atkinson Hyperlegible and Comic Neue for $14.99 one-time