Customizing Accessibility for Users with Dyslexia

Dyslexia affects how the brain processes written language, making reading slower and more effortful for roughly one in ten people. Most websites are built with reading fluency in mind, which means they become friction points for dyslexic users, causing them to bounce, abandon forms, or miss key information. But accessibility customizations specifically designed for dyslexia can transform comprehension, reduce cognitive load, and keep visitors engaged longer.

TL;DR: Dyslexia-friendly accessibility features include adjustable font sizes and letter spacing, high-contrast color options, readable font families (sans-serif, open letterforms), and text-to-speech integration. These customizations improve reading speed and comprehension without harming the experience for non-dyslexic users. Real educational platforms like Newsela and Readability demonstrate that accessible design is good design.

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Understanding Dyslexia and Reading Barriers

Dyslexia is a neurodevelopmental condition that affects phonological processing, the ability to recognize and manipulate sound patterns in language. It's not about intelligence, laziness, or poor eyesight. People with dyslexia often reverse letters, skip words, lose their place on a line, or read at half the typical speed. On top of that, they typically experience higher cognitive load while reading because more mental effort goes to decoding letters and words instead of understanding meaning.

"It affects men and women in equal numbers, between 10 and 15 percent of the population has dyslexia."

>, Improving Websites for People with Dyslexia

When you apply this to web design, the friction becomes real. Dense paragraphs, small fonts, poor color contrast, serif typefaces (with decorative lines), and automatic text-to-speech features that don't exist all combine to create a barrier. A dyslexic user might spend three minutes reading what a non-dyslexic user reads in 30 seconds, and they're likely to give up before reaching the call-to-action.

The good news: customizable accessibility features address these barriers directly. They don't require a complete redesign. They work alongside your existing design, activated by user preference or a simple toggle, and they benefit everyone, not just people with dyslexia.

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Adjustable Font Sizes and Letter Spacing

Larger fonts alone don't fully solve readability for dyslexic users, but they're a critical starting point. Text that's at least 16 pixels on desktop and properly sized on mobile gives readers more visual separation between letters and reduces the scanning load. Beyond size, letter spacing and line height are equally important.

When letters are spaced too tightly together, dyslexic readers confuse similar shapes, the classic "d" and "b" swap, or "rn" reading as "m". Increasing letter spacing by 0.12–0.25 em (typically 2–5 pixels depending on font size) creates breathing room. Line height should be at least 1.5, ideally 1.8, so readers don't lose their place when jumping from the end of one line to the beginning of the next.

Implement this in three ways:

1. Provide a font-size toggle in your header or settings menu with options like small, normal, large, and extra large. Use CSS variables to update font-size, letter-spacing, and line-height simultaneously.
2. Use a readable default font size for all body text, 14–16 pixels minimum. Many sites use 12 px, which is too small for dyslexic readers and strains all readers.
3. Add a "dyslexia-friendly mode" button that sets font-size to 18px, letter-spacing to 0.2em, and line-height to 1.8. Users shouldn't have to hunt for accessibility controls; they should be visible and easy to activate.

body.dyslexia-friendly {
  font-size: 18px;
  letter-spacing: 0.2em;
  line-height: 1.8;
}

This approach maintains your design while removing cognitive barriers. The investment in CSS is minimal; the impact on comprehension is measurable.

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Color Contrast and Background Options

High contrast between text and background is essential for dyslexic readers. While WCAG AA requires a 4.5:1 contrast ratio (often met by black text on white), many dyslexic users benefit from even higher contrast, 7:1 or higher. Some prefer inverted color schemes (white text on dark backgrounds), others prefer tinted backgrounds that aren't pure white.

The reason: pure white backgrounds can cause visual stress and halation (a halo effect around text that makes letters blur). Warm tinted backgrounds, soft beige, cream, or pale yellow, reduce glare and allow readers to sustain focus longer. Dark modes with high-contrast text also work well for readers with light sensitivity or those who read at night.

Offer these contrast and background options:

• Default: Your standard design (black/dark text on white).
• High contrast: Black text, pure white background, bolder font-weight.
• Dark mode: White or light text on dark gray or near-black, high contrast preserved.
• Tinted background: Dark text on soft beige, pale yellow, or soft green background (no pure white).

Many platforms like GitHub, Slack, and educational sites now offer these out of the box. You can build this with a simple CSS class system:

body.contrast-high {
  background-color: #ffffff;
  color: #000000;
  font-weight: 600;
}

body.dark-mode {
  background-color: #1a1a1a;
  color: #ffffff;
}

body.tinted-bg {
  background-color: #fffaf0;
  color: #333333;
}

Add a toggle in your header that saves the user's choice in localStorage so their preference persists across sessions. This small feature signals to visitors that you understand their needs.

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Font Family Selection

Serif fonts (with decorative lines like Times New Roman) make letter recognition harder for dyslexic readers because the extra details create visual noise. Sans-serif fonts with open, clear letterforms, like Arial, Helvetica, Verdana, or Open Sans, are significantly more readable.

Better still are fonts explicitly designed for dyslexia:

• OpenDyslexic: A free, open-source typeface with exaggerated letterforms and heavier bottom weights to anchor letters.
• Dyslexie: A commercial font designed by a dyslexic designer, with distinct letter shapes to prevent reversals.
• Lexend: A variable font family optimized for reading fluency; it adjusts letter spacing and character sizing automatically based on the content.

You don't need to replace your entire design with these fonts. Use them for body text and long-form content while keeping your brand font for headings. The majority of users won't notice the change, but dyslexic readers will experience a measurable difference in reading speed and comprehension.

To include OpenDyslexic, add this to your stylesheet:

@import url('https://fonts.googleapis.com/css2?family=OpenDyslexic&display=swap');

body.dyslexia-friendly {
  font-family: 'OpenDyslexic', sans-serif;
}

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Text-to-Speech Integration

Text-to-speech (TTS) is transformative for dyslexic users because it bypasses the phonological processing bottleneck. When content is read aloud while text is highlighted, users can follow along without the struggle of decoding each letter. This combination of auditory and visual input strengthens comprehension and reduces cognitive fatigue.

Effective TTS implementation includes:

1. Word-level highlighting: As each word is spoken, highlight it visually so the reader stays synchronized.
2. Adjustable playback speed: Users should control how fast the audio plays, some prefer 0.8x speed (slower, clearer), others prefer 1.5x (faster).
3. Natural-sounding voices: Browser-based TTS has improved dramatically. Use voices like Google Chrome's "Google English US" or web-based services like ReadSpeaker or Speechify for higher quality.
4. Easy activation: Place a "Listen" or "Read Aloud" button near the top of each article or content block, not hidden in a menu.

Implement basic TTS using the Web Speech API:

const text = document.querySelector('article').innerText;
const utterance = new SpeechSynthesisUtterance(text);
utterance.rate = 1.0; // adjustable
speechSynthesis.speak(utterance);

For production, consider integrating a dedicated service like ReadSpeaker or Speechify, which offer better voice quality, fine-tuned performance, and analytics on usage.

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Real-World Examples in Education

Educational platforms face dyslexic readers constantly, which is why they've become leaders in accessible customization. Newsela, a platform for K-12 literacy, offers adjustable font sizes, dyslexia-friendly fonts, and optional text-to-speech. Lexia Reading Core5, an intervention program, includes built-in TTS and visual feedback. Readability platforms like Epic! and Learning Ally (formerly LightSail) combine customizable text styling with human-narrated or high-quality synthetic audio.

The pattern is consistent: accessibility features are positioned as enhancements to the core experience, not afterthoughts. Buttons are visible. Settings are intuitive. Once a user activates a feature, it stays on by default for future sessions. These platforms also noticed that non-dyslexic users, ESL learners, auditory learners, people reading in noisy environments, use the same features. Accessibility features aren't charity; they're intelligent product design.

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Measuring the Impact of Customizations

How do you know if your accessibility work is paying off? Track these metrics:

• Session duration: Users with dyslexia typically have shorter sessions on sites with poor readability. After implementing customizations, track whether average session time increases, especially for users who activate accessibility features.
• Bounce rate: Compare bounce rate for visitors who use the dyslexia-friendly mode versus those who don't. You should see a lower bounce rate for the enabled group.
• Comprehension tasks: If your site includes forms, quizzes, or sign-ups, track completion rates. Accessible text should improve task completion.
• Return rate: Accessible sites see higher return-visitor rates. If users feel respected and can actually read your content, they come back.
• Feature adoption: Monitor how many visitors activate accessibility features. Low adoption might mean the controls aren't visible or intuitive enough.

Use heatmaps (Hotjar, Crazy Egg) and session recordings (FullStory, LogRocket) filtered by users who activated dyslexia-friendly mode to see how they interact with your site. Do they scroll smoothly, or do they jump? Do they linger on key sections, or skip past them?

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Key Takeaway

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FAQ

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Additional Resources

• Improving Websites for Users with Dyslexia - Making content more accessible for users with dyslexia · Make text left-aligned (not fully justified) · Use a sans-serif font.
• Designing for Dyslexia: Accessibility Requirements and Best ... - Designing for dyslexia is about reducing reading effort and creating flexibility. Tools like HelperBird, thoughtful magnification with reflow, ...
• How To Design For Users With Dyslexia - Avoid dynamic, moving or flashing images. · Avoid heavy underlines, uppercase and italics. · Don't force users to remember; give reminders instead. · Avoid text ...

The opportunity is clear: visitors with dyslexia represent 10–15% of your potential audience. When you customize accessibility for them, you're not just being inclusive, you're removing a barrier to conversion and engagement that competitors probably haven't addressed. What's one accessibility feature you could implement this week to test with dyslexic readers?