Legibility and readability sound like two ways of saying the same thing. They aren’t. Legibility is about how easily you can recognise individual letters and words; readability is about how comfortably you can keep reading them.
Typography has a few terms that sound more complicated than they really are. Legibility and readability are two of them.
They’re closely related, but they’re not the same thing. Not exactly edge-of-your-seat material, granted. But if you’re new to design, pay attention. This is the sort of thing that quietly makes your work better.
What is legibility?
Legibility is how quickly you can look at a word and recognise what it says without having to decipher it.
A word becomes more legible when its letters have clear, familiar shapes, enough space between them and useful contrast.
Hamburger is easy to recognise when the letters remain distinct. Squash them together, make them tiny or use similar shapes, and it takes more effort to understand.
Uppercase works well when the message is short and needs immediate impact: EXIT, SALE, BREAKING NEWS.
Over longer passages, sentence case is easier to follow because the letter shapes vary more. That’s why a newspaper can shout across a front page in capitals without setting the entire paper that way.
These three front pages show legibility at its bluntest: the message is unmistakable, Diana dead, and the impact hits you immediately.
Certain characteristics of a typeface can make words easier or harder to recognise:
- Clear differences between similar characters
- Open counters and apertures
- An appropriate x-height
- Sensible character spacing
- Enough distinction between shapes
- Suitable stroke weight
- Clear punctuation and numerals
Some characters are surprisingly easy to confuse, especially at small sizes or in poorly designed typefaces. The classic examples are uppercase I, lowercase l and the number 1, or uppercase O and zero.
Good legibility depends on giving similar shapes enough visual difference that the reader can identify them instantly.
What is readability?
Readability describes how easily someone can follow a complete passage of text rather than how clearly they can identify individual letters or words.
Lines that are too long make it harder to locate the beginning of the next one.
Tight leading causes neighbouring lines to compete for attention.
Centred text removes the consistent starting point that longer passages need, while weak contrast makes the reader work harder than necessary.
The problem isn’t always immediately obvious.
It appears as friction: you lose your place, reread a line or stop reading sooner than you intended.
Across several paragraphs, those small interruptions accumulate.
Readability is influenced by:
- Line length
- Font size
- Leading
- Paragraph spacing
- Contrast
- Hierarchy
- Alignment
- Column width
Typography can make words easier to read, but it can’t make bad writing clear. A paragraph might be beautifully set, with comfortable line spacing and perfect contrast, but if the sentences are confusing or unnecessarily complicated, the reader still has to work hard.
You can get one right and the other wrong
A typeface can be perfectly legible at headline size but exhausting over a long article. The letters are clear; the reading experience isn’t.
The reverse is also true. A well-designed typeface can become difficult to read if it’s too small, too light or badly spaced.
That’s the point: the typeface matters, but the way it’s used matters just as much.
Different situations need different things
A road sign or safety warning needs immediate recognition.
“Danger of death” isn’t exactly leaving the door open for interpretation. High contrast, familiar warning symbol, blunt wording. You read it once and your brain goes: right, probably don’t touch that.
A novel has a very different job. It needs to remain comfortable for hundreds of pages.
A food package might have a few seconds to tell you what it is from the other side of a supermarket aisle.
Classic advertising makes the same point. Volkswagen’s “Lemon” advert uses Futura, short copy blocks and a brutally clear headline to deliver the message quickly.
A website article has to work across different screen sizes and reading conditions.
The priorities change with the context.
Line length matters more than people think
One of the easiest ways to make otherwise decent typography uncomfortable is to make the text column too wide.
Apple’s product pages are a good example of short line lengths used well: the copy is brief, the measure is controlled, and each block is easy to scan on a phone screen.
When a line becomes very long, your eye has farther to travel before finding the beginning of the next one.
Too narrow and the opposite happens. You’re constantly jumping onto a new line.
For ordinary body text, somewhere around 45 to 75 characters per line often provides a useful starting point.
It isn’t a law.
Hit 76 characters and nobody’s going to kick the door in shouting, “Step away from the paragraph!”
But it’s a useful range to test.
Leading affects readability
Leading, or line spacing, has a huge effect on readability.
Set lines too tightly and paragraphs become dense blocks.
Set them ridiculously far apart and the lines stop feeling connected.
The right amount depends on the typeface, size, line length and intended use.
Fonts with a large x-height may need different spacing from delicate serifs with long ascenders and descenders.
There isn’t one magic percentage.
Look at the paragraph rather than blindly obeying whatever your design software suggests.
Contrast affects readability
Black text on white gives extremely strong contrast.
That doesn’t mean everything has to look like it’s been designed by HMRC on a wet Tuesday.
But when contrast becomes too weak, reading becomes harder.
Light grey body copy on white became fashionable on websites for a while because apparently being able to read things was considered slightly vulgar.
It can look elegant on a designer’s enormous calibrated monitor.
Put it on a phone in daylight and suddenly that tasteful grey text is playing hide-and-seek. Brilliant.
Readability changes with the audience
Age, eyesight, screen quality, lighting conditions and reading ability can all affect how typography performs.
What looks obvious to the person designing something isn’t automatically obvious to the person reading it.
Test text at the size and distance people will actually read it. If it only works when you zoom in, it isn’t working.
A five-minute legibility and readability check
Before you approve a design, ask yourself:
Legibility
- Can similar characters be distinguished easily?
- Is the text large enough for its intended use?
- Is there enough contrast?
- Has tracking become too tight?
- Do important words remain clear from the expected viewing distance?
Readability
- Are the lines comfortable to follow?
- Is there enough leading?
- Are paragraphs broken into manageable chunks?
- Is the hierarchy obvious?
- Does alignment help rather than fight the reader?
Read it.
Read the whole thing at its intended size. You’ll spot problems quickly.
You’ll find slightly different definitions depending on which typography book you pick up. Course you will. Typography loves a committee. But the useful bit is simple: legibility is recognising the words; readability is managing to stay with them.
The distinction matters because font choice alone doesn’t determine how well text reads. A well-designed typeface can still perform badly when size, spacing, line length or contrast are wrong; a less obvious typeface can work extremely well when those conditions are handled properly.
Frequently asked questions
What is the difference between legibility and readability?
Legibility describes how easily individual letters, characters and words can be recognised. Readability describes how comfortably larger amounts of text can be read.
What makes a font legible?
Clear character shapes, distinguishable letters, open counters, appropriate spacing and suitable proportions can all improve legibility. Size, colour and contrast also affect how legible the type appears in use.
What makes text readable?
Readable typography usually combines appropriate font choice, comfortable line length, suitable leading, good contrast, clear hierarchy and sensible paragraph structure.
Can a decorative font be legible?
Yes. A decorative typeface can have extremely clear individual characters while still being unsuitable for long passages of text.
Does uppercase text improve legibility?
Uppercase can improve recognition and impact in short messages such as signs and headlines, but long passages of uppercase text are generally harder to read comfortably. Sentence case usually works better for continuous reading.
Is serif or sans serif more readable?
There isn’t a universal winner. Both serif and sans-serif typefaces can work extremely well for reading when they’re designed and typeset appropriately.
Context, size, spacing and medium often matter more than simply whether the letters have serifs.
Why does line length affect readability?
Very long lines make it harder for the eye to find the beginning of the next line. Very short lines interrupt reading too frequently. A moderate line length helps the eye move through a paragraph more comfortably.
What is a good line length for body text?
Around 45 to 75 characters per line is a useful starting point for many types of continuous text, although the ideal measure varies with typeface, font size and format.
About Simon Stratford
I’m Simon Stratford, an independent type designer creating display fonts, SVG fonts and typefaces for designers, brands and creative projects.
I write about typography, font design, graphic design and the occasionally peculiar decisions we all make when letters get involved.