Line Spacing, Letter Spacing and Readability: A Practical Guide
How much space between lines, letters and words makes text easier to read? The WCAG numbers, the dyslexia research, and settings you can try today.
When text feels dense or tiring, most people reach for a bigger font size. Often the real fix is space: between lines, between letters and between words. Spacing is also one of the best-researched ways to help readers with dyslexia.
The four kinds of spacing
- Line spacing (line height or leading): the vertical distance from one line to the next.
- Letter spacing (tracking): the gap between every letter in a word.
- Word spacing: the gap between words.
- Paragraph spacing: the gap after each paragraph.
Web designers often tighten all four to make pages look sleek. That can be fine for short headlines, and hard work for long reading.
What the accessibility standards say
The Web Content Accessibility Guidelines (WCAG) give two useful reference points.
WCAG 1.4.12 Text Spacing (Level AA) says a website must still work when a reader overrides spacing to:
| Setting | Value (× font size) |
|---|---|
| Line height | 1.5 |
| Spacing after paragraphs | 2 |
| Letter spacing | 0.12 |
| Word spacing | 0.16 |
These aren’t targets for designers. They are the minimum amounts of extra spacing a reader should be able to apply without the page breaking. W3C wrote them for people with low vision and dyslexia who need more space to read.
WCAG 1.4.8 Visual Presentation (Level AAA) goes further: line spacing of at least 1.5 within paragraphs, lines no wider than 80 characters, and no fully justified text, which creates uneven gaps between words.
What the research says about dyslexia
In 2012, Marco Zorzi and colleagues tested Italian and French children with dyslexia. Simply increasing the spacing between letters improved reading speed and accuracy on the spot, with no training. The explanation is crowding: letters packed close together interfere with each other, and many dyslexic readers are especially sensitive to it.
The British Dyslexia Association style guide makes similar recommendations for everyday documents: line spacing of 1.5, left-aligned text, sans serif fonts and short paragraphs.
Settings to try
Start here, then adjust one setting at a time:
- Line height: 1.5. If lines still blur together, try 1.7. Above 2, paragraphs start to fall apart.
- Letter spacing: 0.05 to 0.12 em. A little goes a long way. Stop before words start to look like separate letters.
- Word spacing: usually follows letter spacing. Increase it slightly if words run together.
- Line length: 60 to 75 characters. On a phone this happens naturally. On a Mac, narrow the window or use Reader.
- Left-aligned text. Avoid justified text, which stretches the gaps between words unevenly.
Try it now
Our dyslexia page has a live preview. Drag the line and letter spacing sliders and watch a paragraph change, then share the link to your favorite settings.
Why Safari can’t do this on its own
Safari has no setting for line or letter spacing on normal web pages. Reader view improves spacing a little on articles, but you can’t adjust it, and it doesn’t work on most sites.
FontFlex adds spacing controls to Safari on iPhone, iPad and Mac. Set line height, letter spacing and font weight once and every website follows them, alongside your choice of font and text size.
When a site breaks
Because WCAG 1.4.12 only became a requirement in 2018, some older sites weren’t built to handle extra spacing. You might see text overlapping or cut off with “…”. If that happens:
- Reduce line height slightly for that site with a separate profile.
- Or turn FontFlex off for that one site from the Safari toolbar menu.
Summary
- Spacing often helps more than size alone.
- Start with 1.5 line height and a little letter spacing, then adjust.
- The evidence for extra letter spacing is strongest for readers with dyslexia.
- Keep lines short and text left-aligned.
