Dyslexia-Friendly Fonts: What Research Actually Shows

Few topics in typography generate more confident misinformation than dyslexia-friendly fonts. Search for guidance on the subject and you will find definitive-sounding claims: that fonts with weighted letter bottoms prevent reversals, that increased letter spacing is essential, that a particular commercial font will dramatically improve reading speed. Many of these claims are marketed more than they are researched.

This guide examines what peer-reviewed research actually shows about typography and dyslexia, what properties genuinely help, and how to implement practical CSS that benefits dyslexic readers without requiring a subscription to a specialized font service.

The Science of Reading and Dyslexia

Dyslexia is a specific learning disability characterized by difficulty with accurate and fluent word recognition, poor spelling, and poor decoding abilities. It is neurological in origin — fMRI studies have shown consistent differences in how dyslexic readers activate areas in the left hemisphere involved in phonological processing. Dyslexia is not a vision problem, not a sign of low intelligence, and not caused by reading letters "backwards," though letter reversal is a symptom some dyslexic readers experience.

Prevalence estimates range from 5% to 17% of the population, depending on the diagnostic criteria used. The wide range reflects genuine disagreement in the field about where to draw the diagnostic threshold, not measurement error. Even at the low end, 5% represents hundreds of millions of people globally who experience significant reading difficulty.

The core deficit in most forms of dyslexia is phonological: difficulty mapping written symbols to the sounds they represent. This is important for understanding typography's role — or rather, its limits. No font can improve phonological processing. Typography cannot reteach the brain to decode written language. What typography can do is reduce the visual processing burden, freeing up cognitive resources for the more demanding phonological work.

Visual processing challenges that typography can address include:

• Crowding: The tendency for surrounding letters to interfere with identification of a target letter. This is reduced by increased letter spacing.
• Character confusion: Visually similar letterforms (b/d, p/q, n/u, m/w) are more frequently confused by dyslexic readers. Font designs that increase the distinctiveness of these characters reduce error rates.
• Tracking errors: Losing one's place on a line or jumping to the wrong line. This is addressed by appropriate line height and line length.
• Orthographic consistency: The degree to which letter forms are uniform and predictable affects decoding speed.

Dedicated Dyslexia Fonts: Do They Help?

The most famous dyslexia-specific font is OpenDyslexic, a free, open-source typeface designed by Abe Cooke. It features heavily weighted bottoms on letterforms — the idea being that letters will be less likely to "flip" because one end is visually heavier. Other commercial options include Dyslexie (by Christian Boer), Lexie Readable, and Read Regular.

The marketing claims for these fonts are significant: faster reading speed, fewer errors, greater comfort. The research evidence is considerably more modest.

A systematic review published in Dyslexia (the journal) in 2017 examined multiple studies comparing specialized dyslexia fonts against standard fonts. The conclusion: there is no strong evidence that specialized dyslexia fonts improve reading speed or accuracy over conventional fonts that share their visual properties (good character differentiation, adequate spacing, simple letterforms). A 2019 study specifically testing OpenDyslexic against Arial found no significant difference in reading speed or accuracy for dyslexic readers, and some non-dyslexic readers actually read more slowly with the specialized font.

A 2020 study in PLOS ONE tested Dyslexie font against Arial, adjusting for spacing to isolate the font design itself. Again, no significant advantage was found for the dyslexia-specific font.

This does not mean dedicated dyslexia fonts are useless. Some dyslexic readers report strong subjective preference for OpenDyslexic and find it more comfortable, even if objective reading speed measurements do not show improvement. User-reported comfort and preference are legitimate accessibility considerations — if a user prefers a font, they are more likely to actually read the content. However, the evidence does not support mandatory adoption of these fonts over well-designed standard alternatives, and the unusual letterforms of fonts like OpenDyslexic may actually reduce reading speed for non-dyslexic readers.

What Research Actually Recommends

If specialized dyslexia fonts do not have strong evidence behind them, what does the research support?

The British Dyslexia Association's style guide, which synthesizes existing research, recommends the following:

• Use sans-serif fonts: Not because serifs are inherently bad, but because many commonly used serif fonts have inconsistent stroke weights and decorative features that increase visual complexity. Simple, well-designed serifs like Source Serif 4 can be fine; ornate ones should be avoided.
• Use larger font sizes: 12–14pt is their recommendation for print; the web equivalent is at least 1rem (typically 16px) with 1.25rem preferred for body text.
• Use good character spacing: Both inter-letter and inter-word spacing should be generous. The research is consistent on this point.
• Use adequate line spacing: 1.5 times the font size is a commonly cited recommendation.
• Avoid justified text: Rivers of whitespace disrupt reading flow for dyslexic readers more than for others.
• Limit line length: 60–70 characters per line.
• Use high contrast: Not strictly a dyslexia recommendation, but poor contrast compounds reading difficulty.

The University of British Columbia's research group found that the most impactful single change for dyslexic readers was increased character spacing — more so than font choice. A well-spaced Helvetica outperformed a poorly spaced dedicated dyslexia font.

A 2012 study by Zorzi et al. in PNAS found that increasing inter-letter spacing by 2.5 points (roughly 0.08em at body text sizes) reduced reading errors significantly for dyslexic children. The effect was not present for non-dyslexic readers, suggesting this specific spacing adjustment is particularly relevant for dyslexic readers.

Font Properties That Aid Dyslexic Readers

Given the evidence, we can identify specific font properties that are likely to aid dyslexic readers — properties shared by many standard fonts that are freely available.

High x-height: A tall x-height (the height of lowercase letters relative to capitals) increases the visual size of text without increasing the nominal font-size. It also tends to produce clearer lowercase letterforms. Inter, Roboto, and Open Sans all have relatively high x-heights. This is one reason these fonts are often preferred for UI and body text.

Distinct letterforms for commonly confused characters: The b/d/p/q problem is real for some dyslexic readers. Fonts that make these characters visually distinct through differences in bowl shape, stroke direction cues, or seriffed elements help. Verdana uses slight stem differences that aid differentiation. Inter in its default setting has a hooked lowercase L and a serifed capital I, which helps with l/I/1 confusion though not with the rotational b/d/p/q problem.

Consistent stroke weight: Fonts with high contrast between thick and thin strokes (classical serifs, Display typefaces) create varying visual density that can complicate letter identification. Low-contrast fonts — most sans-serifs, humanist designs — are more uniform and easier to scan.

Generous default spacing: The font's built-in tracking (letter-spacing) affects readability before any CSS is applied. Fonts designed for text use (as opposed to display or headline use) typically have spacing optimized for reading. Comparing Open Sans and a condensed variant at the same CSS font-size, the standard version is noticeably easier to read at length.

No italics for long passages: Italic letterforms are more cursive and more variable than their roman counterparts. Research suggests dyslexic readers find italics harder to decode. Use italics sparingly — for titles, citations, and occasional emphasis — never for body text.

Consistent baseline alignment: Fonts with irregular baseline positioning (some handwriting-style fonts, some display fonts) add visual noise that increases cognitive load.

Practical CSS for Dyslexia-Friendly Typography

You do not need a specialized font to implement dyslexia-friendly typography. The following CSS establishes a solid accessible baseline using freely available fonts:

/* Base dyslexia-friendly typography settings */
body {
  font-family: 'Open Sans', 'Roboto', Arial, sans-serif;
  font-size: 1.125rem;      /* 18px at default — slightly larger than minimum */
  font-weight: 400;          /* Regular weight — avoid Light for body text */
  line-height: 1.6;          /* 1.5–1.8 range is well-supported by research */
  letter-spacing: 0.05em;    /* Slight increase from default improves word spacing */
  word-spacing: 0.1em;       /* Generous word spacing aids word boundary recognition */
  text-align: left;          /* Never justify */
  color: #1a1a1a;
  background-color: #fefefe;
}

/* Paragraph width */
.content {
  max-width: 70ch;           /* 60–80 characters per line */
  margin: 0 auto;
}

/* Paragraph spacing */
p {
  margin-bottom: 1.5em;
}

/* Headings: slightly looser spacing */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;          /* Clear weight distinction from body */
  line-height: 1.25;
  letter-spacing: 0.02em;
  margin-top: 1.5em;
  margin-bottom: 0.5em;
}

/* Avoid italics in body content */
em {
  font-style: normal;
  font-weight: 600;          /* Use weight instead of italic for emphasis */
}

/* Don't underline text that isn't a link */
.non-link-emphasis {
  text-decoration: none;
  border-bottom: 2px solid currentColor; /* Underline effect without font italics */
}

For users who have explicitly indicated a preference for specific typography — via a site preference panel or operating system settings — you can use CSS custom properties to allow overrides:

:root {
  --font-family: 'Open Sans', sans-serif;
  --font-size: 1.125rem;
  --line-height: 1.6;
  --letter-spacing: 0.05em;
}

/* High-legibility mode toggle */
.high-legibility {
  --font-family: 'OpenDyslexic', 'Comic Sans MS', sans-serif;
  --font-size: 1.25rem;
  --line-height: 1.8;
  --letter-spacing: 0.1em;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size);
  line-height: var(--line-height);
  letter-spacing: var(--letter-spacing);
}

Using prefers-reduced-motion and prefers-color-scheme shows precedent for respecting user preferences at the CSS level. A custom preference panel for typography — offering larger text, increased spacing, or alternative fonts — follows the same principle of user control over their reading environment.

The Reading Ruler concept is also worth implementing for text-heavy applications. A CSS-based highlight of the current line or paragraph as the user reads can help dyslexic users maintain their place:

/* Line highlighting on focus/hover for reading assistance */
p:focus-within {
  background-color: rgba(255, 255, 0, 0.15);
  border-radius: 2px;
  outline: none;
}

Recommended Fonts and Settings

Based on the research and practical accessibility considerations, here are specific font recommendations across different availability tiers:

Google Fonts (free, widely available)

Open Sans is one of the most commonly recommended fonts for dyslexic readers among practitioners. Its humanist design has a high x-height, wide apertures, and clear character differentiation. The letter spacing in the default variant is already generous. Set it at 1.125–1.25rem, weight 400, line-height 1.6–1.8.

Roboto is structurally similar to Open Sans with some geometric influences. Slightly more uniform letterforms make it fractionally less distinctive in ambiguous characters, but it remains a solid accessible choice. The flex between light and medium weights is useful for establishing hierarchy without italics.

Source Sans 3 (formerly Source Sans Pro) was designed for Adobe with UI legibility as a priority. Its character differentiation is excellent — the lowercase a, g, and other potentially ambiguous forms are clearly distinct from each other. Available in a wide weight range including a variable font version.

Atkinson Hyperlegible deserves specific mention. Developed by the Braille Institute, it was explicitly designed for readers with low vision, with differentiated letterforms as a primary design goal. Research studies on this specific font show measurable improvements in reading accuracy for low-vision readers. Unlike most "accessibility fonts," it is also genuinely well-designed typographically — attractive at display sizes, clear at body sizes.

System Fonts

-apple-system (San Francisco on macOS/iOS) and Segoe UI (Windows) are both excellent accessible fonts with the advantage of maximum familiarity to their respective platform users. For a system font stack:

font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
             'Open Sans', Arial, sans-serif;

Specialty Fonts

OpenDyslexic is available free and open-source. If your user base includes a high proportion of dyslexic readers, offering it as an opt-in alternative is valuable. Its unusual letterforms limit its usefulness as a default, but user control over font choice is a strong accessibility principle.

The most important principle across all font recommendations: offer user control. Research shows that individual dyslexic readers vary enormously in what helps them. Some benefit from larger text, some from increased spacing, some from specific fonts, some from colored overlays. The best accessible typography system is one that lets users adjust their own experience — not one that assumes a single optimal configuration for all dyslexic readers.