Bionic Reading Chrome Extension That Bolds the First Half of Every Word

What bionic reading actually is

Bionic reading is a text formatting technique where the first few letters (usually half) of each word are bolded. The idea is that your eyes fixate on the bold anchor, your brain recognizes the word, and you move forward without having to sound out each letter fully.

The technique was coined by Renato Casuut and is designed to increase reading speed while reducing mind-wandering. Whether it works varies by person, but for a lot of readers — especially those with ADHD or dyslexia — the bold anchors act like visual stepping stones that keep their eyes moving in the right direction.

The problem with existing bionic reading tools

The official Bionic Reading API is paid and mostly aimed at publishers. As a reader, you can't just flip it on for random web pages. There are a few userscripts floating around, but they require Tampermonkey, break on pages with complex formatting, and don't have any settings to adjust.

More importantly, bionic reading alone isn't always enough for people who struggle with reading focus. It needs to be combined with other tools — like line focus or reading mode — to be genuinely useful.

How the Chrome extension approach works

ADHD Reading Focus implements bionic reading directly in Chrome through a content script. When you enable it, the extension walks the DOM of the current page and splits every word's text node so the first half is wrapped in a bold span.

It's careful not to break interactive elements — it targets readable content areas and avoids buttons, form inputs, code blocks, and navigation. This matters a lot because naive implementations mess with page layout.

The processing is fast enough that you don't see a flash or reflow on most pages. On extremely long pages (50,000+ words), there's a brief moment — but it's negligible.

Turning it on

Install ADHD Reading Focus from the Chrome Web Store. Navigate to any article or long-form page. Click the extension icon in your toolbar.

You'll see a Bionic Reading toggle. Switch it on. The page reformats immediately.

If the default bold intensity feels too heavy, there's a slider to adjust how many characters get bolded per word. Some people prefer just 2 characters. Others want 50% of every word. Try a few settings and see what feels natural to your eyes.

You can also enable it globally so it applies on every page automatically, or leave it manual and trigger it only when you want to read something carefully.

Who benefits most

Bionic reading tends to help most with:

• Readers who get to the end of a sentence and realize they didn't absorb a word of it
• People with ADHD whose eyes drift off the line mid-sentence
• People with dyslexia who find the bold anchors reduce decoding effort
• Anyone reading in a second language, where word recognition speed is slower

It's less useful for highly technical content with lots of jargon, because the bold anchor only helps if your brain already knows the word. When the words are unfamiliar, you need to read them fully regardless.

Combining it with line focus

The most powerful combination is bionic reading plus line focus mode. Bionic reading keeps your eyes on the words. Line focus keeps them on the right line. Together, they create a reading experience that feels almost like a guided path through the text.

If you've tried bionic reading before and found it only marginally helpful, try pairing it with line focus. The difference is significant.

Conclusion

Bionic reading isn't a silver bullet, but it's a genuine tool that helps a lot of people read faster and with less mind-wandering. Having it available directly in Chrome — without copying text into another app or paying for a subscription — makes it practical enough to actually use.