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Low Vision Font Guide

Comprehensive font recommendations for users with low vision. Learn optimal font sizes, high contrast requirements, magnification-friendly typography, sans-serif recommendations, and best practices for partially sighted users.

TL;DR - Key Takeaways

  • • Minimum 18-20px font size for body text, 24px+ preferred for low vision users
  • • Sans-serif fonts (Arial, Verdana, Helvetica) with clean letterforms work best
  • • High contrast (7:1 or higher) reduces eye strain for low vision users
  • • Generous letter and line spacing prevents crowding under magnification

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According to the World Health Organization, approximately 246 million people globally have moderate to severe vision impairment. Low vision, defined as visual acuity between 20/70 and 20/400 or significant visual field loss, affects people's ability to read, navigate, and interact with digital content. Unlike blindness, people with low vision retain some functional sight and can often read text if it's properly formatted with adequate size, contrast, and spacing.

Typography plays an enormous role in accessibility for low vision users. While screen readers assist blind users, people with low vision primarily access content visually, making font choice, size, weight, and spacing critical factors in usability. Poor typography creates barriers that force low vision users to abandon content or struggle unnecessarily, while thoughtful typography enables comfortable, efficient reading.

Low vision encompasses diverse conditions: macular degeneration (central vision loss), glaucoma (peripheral vision loss), diabetic retinopathy (patchy vision loss), cataracts (blurred vision), and albinism (reduced contrast sensitivity). Each condition creates different challenges, but certain typographic principles benefit all low vision users: generous sizing, high contrast, clean letterforms, adequate spacing, and scalability.

This guide explores font selection for low vision accessibility, optimal sizing strategies, contrast requirements beyond WCAG minimums, magnification considerations, spacing and layout recommendations, and techniques for creating flexible typography systems that accommodate diverse vision capabilities. Whether designing websites, mobile apps, or digital documents, implementing these principles dramatically improves accessibility for millions of users with vision impairments.

Understanding Low Vision and Typography Needs

Low vision users face specific challenges when reading digital text that inform typography requirements.

Reduced Visual Acuity

Visual acuity measures the sharpness of vision. Normal vision is 20/20, meaning you can see at 20 feet what someone with typical vision sees at 20 feet. Low vision ranges from 20/70 (legally impaired) to 20/400 (severe impairment). At 20/200, text appears blurry as if viewing it through heavy fog or frosted glass.

Typography Impact:

  • Small text becomes illegible—minimum 18-20px needed
  • Thin font weights disappear—use medium (500) or bold (700) weights
  • Fine details blur—avoid decorative fonts with thin serifs
  • Letter confusion increases—use fonts with distinct letter shapes

Reduced Contrast Sensitivity

Contrast sensitivity—the ability to distinguish between similar shades—declines with many vision conditions. Text that appears clearly readable to fully sighted users may be nearly invisible to users with reduced contrast sensitivity.

Typography Impact:

  • WCAG minimum 4.5:1 contrast often insufficient—aim for 7:1 or higher
  • Avoid gray text—use near-black (#222) instead
  • Pure black on pure white can cause glare—use off-black on off-white
  • Background patterns make text harder to read

Visual Field Loss

Conditions like glaucoma cause peripheral vision loss (tunnel vision), while macular degeneration causes central vision loss (blind spot in center). Users must piece together text from limited field of view.

Typography Impact:

  • Generous line height (1.8-2.0) prevents line confusion
  • Moderate line length (50-70 characters) easier to track
  • Left-aligned text with ragged right edge aids navigation
  • Clear paragraph breaks provide visual anchoring points

Screen Magnification Challenges

Many low vision users use screen magnification software (200-400% zoom or higher). Magnification reveals typography flaws invisible at default sizes and reduces the amount of text visible at once.

Typography Impact:

  • Tight letter spacing becomes crowded—use 0.05-0.1em letter-spacing
  • Font rendering quality matters—avoid bitmap fonts
  • Responsive layouts must reflow at high zoom levels
  • Clear headings and structure aid navigation with limited viewport

Font Size Requirements for Low Vision

Font size requirements for low vision users exceed WCAG minimums. While WCAG requires text to scale to 200%, low vision users often need base sizes much larger than typical 16px.

Recommended Minimum Sizes

Body Text: 18-20px

Standard 16px is too small for many low vision users. Start at 18-20px for body text, or provide an easy mechanism for users to increase size.

body {
  font-size: 1.125rem; /* 18px */
}

@media (min-width: 1024px) {
  body {
    font-size: 1.25rem; /* 20px */
  }
}

Headings: 24-48px

Headings should be significantly larger than body text to create clear hierarchy for limited field of view.

h1 { font-size: 3rem; /* 48px */ }
h2 { font-size: 2.25rem; /* 36px */ }
h3 { font-size: 1.75rem; /* 28px */ }
h4 { font-size: 1.5rem; /* 24px */ }

Provide Size Controls

Implement font size controls that allow users to increase text size beyond browser zoom. This provides finer control and better user experience than browser-level zoom.

// Simple font size control
const sizes = ['medium', 'large', 'x-large'];
function setFontSize(size) {
  document.body.classList.remove(...sizes);
  document.body.classList.add(size);
  localStorage.setItem('fontSize', size);
}

/* CSS */
body.medium { font-size: 16px; }
body.large { font-size: 20px; }
body.x-large { font-size: 24px; }

Test at 200-400% Zoom

WCAG requires functionality at 200% zoom (Level AA), but many low vision users operate at 300-400% zoom. Test your layouts at these extreme magnifications to ensure text reflows properly and remains readable. Learn more in our font size requirements guide.

High Contrast Requirements

Low vision users with reduced contrast sensitivity need higher contrast than WCAG minimums.

Aim for AAA Contrast (7:1)

While WCAG AA requires 4.5:1 for normal text, AAA level (7:1) provides significantly better readability for low vision users. When possible, exceed even AAA requirements.

Excellent (15.3:1)

Near-black on white

#1a1a1a on #ffffff

Acceptable (7.2:1)

Dark gray on white

#595959 on #ffffff

Avoid Extreme Contrast in Some Cases

Pure black (#000) on pure white (#fff) at 21:1 can cause glare and halation (light bleeding) for some low vision users. Slightly off-black on slightly off-white often provides better comfort while maintaining excellent contrast.

/* Recommended: High contrast without glare */
body {
  color: #1a1a1a; /* Off-black */
  background: #fafafa; /* Off-white */
  /* Contrast: ~15:1 - excellent readability without glare */
}

Provide High Contrast Mode

Offer a high contrast mode that users can enable for maximum readability. Many operating systems provide high contrast themes that you should respect.

/* Respect OS high contrast preferences */
@media (prefers-contrast: high) {
  body {
    color: #000;
    background: #fff;
  }

  a {
    color: #0000ff;
    text-decoration: underline;
  }
}

Spacing and Layout for Low Vision

Generous spacing prevents crowding and improves readability, especially under magnification.

Letter Spacing: 0.05-0.12em

Increased letter spacing prevents letters from blurring together at high magnification.

Default spacing

Reading text example

0.08em spacing

Reading text example

Line Height: 1.8-2.0

Generous line height prevents lines from crowding together, crucial for users with limited field of view who may lose their place.

body {
  line-height: 1.8; /* 1.8× font size */
}

/* Even more generous for critical content */
.article-content {
  line-height: 2.0;
}

Paragraph Spacing: 2em

Clear paragraph breaks provide visual anchoring points and rest areas for eyes.

p {
  margin-bottom: 2em;
}

/* Don't use first-line indent for low vision */
p + p {
  text-indent: 0; /* Avoid, use margin instead */
}

Line Length: 50-70 Characters

Moderate line length helps low vision users track from end of one line to beginning of next, especially with peripheral vision loss. Use max-width: 65ch to limit line length based on character count.

Best Practices for Low Vision Typography

Use Flexible, Scalable Typography

Implement typography using relative units (rem, em) that scale with user preferences. Avoid fixed pixel sizes that prevent users from adjusting text to comfortable levels.

Test with Screen Magnification

Use built-in screen magnification (macOS Zoom, Windows Magnifier) at 200-400% to verify text remains readable and layouts don't break. This reveals issues invisible at default zoom.

Avoid Text in Images

Text in images doesn't scale cleanly and becomes pixelated at high magnification. Use actual HTML text with CSS styling instead. If images with text are unavoidable, provide extremely high-resolution versions.

Provide Multiple Ways to Adjust Size

Support browser zoom, browser font size settings, and optionally provide custom font size controls. Different users prefer different methods of size adjustment.

Consider System Preferences

Respect OS-level preferences for high contrast, reduced motion, and forced colors. Use CSS media queries like prefers-contrast and forced-colors to adapt.

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Sarah Mitchell

Written & Verified by

Sarah Mitchell

Product Designer, Font Specialist

Low Vision Fonts FAQs

Common questions about fonts for low vision users