Legibility and Readability: What’s the Difference?

There are some terms in typography that are frequently confused with others because they are related in meaning – but still different. Legibility and readability are two of them. These terms are important for designers to know as they contribute to the language used to talk about fonts, typesetting, and design. Legibility and readability both relate to the ease and clarity with which one reads any particular setting of type, but they actually refer to two different concepts: legibility is related to the design of the typeface and the shape of the glyphs, while readability refers to how the font is arranged, or typeset. Both are particularly important when setting text or any smaller type sizes.

Legibility

The legibility of a typeface is a product of its design, and relates to the ability to distinguish one glyph from another when reading. Factors contributing to a typeface’s legibility include the following:

x-height: This term refers to the height of the lowercase in proportion to the caps. The taller the x-height, the more legible the typeface tends to be.

Both text blocks are set in 18 pt, but the one set in Enclave (right) is more legible, primarily due to its taller x-height than ITC Golden Type (left), with its short x-height.

Character width: The easiest type designs to read are those that have an ‘average’ overall width. Very condensed as well as extended designs are less legible, especially for smaller settings such as text, subheads, and credits.

When comparing text set in Clearview Text Book Compressed with that set in Clearview Book, one can see that the version on the right has a greater degree of legibility than the very narrow version to its left.

Weight: Extremely light and heavy weights are more difficult to read, so if legibility is your goal, stick to something in the middle. Book weights (also called Regular) are so named as they are most often used to typeset books for that very reason.

Neither Clearview Text Extra Thin nor the Black weight have the same high degree of legibility for lengthy text that the Book weight has, as seen in the previous example (on the right). Save these weights for shorter settings, and when maximum legibility is not a requirement.

Design traits: The overall shapes and design traits of a typeface, if too quirky or fussy, will reduce legibility. While this might be acceptable for shorter display settings, stick to simpler typeface designs for lengthy text settings.

Stroke contrast: Extreme stroke contrast, that is, the ration of thick to thin strokes, can reduce legibility as well. This is especially true of modern designs such as Bodoni and Didot whose thin strokes can appear so thin when reproduced in print or on the web that it can become challenging to read when used too small or for lots of text.

The extreme stroke contrast of Didot (left) can make it harder to read for small settings, as the thin strokes can seem to disappear at smaller sizes and at lower resolutions.

Counters: The smaller the counters (enclosed or semi-enclosed negative shapes) of a typeface, the more challenging it can be to read. This is a factor when using very heavy weights, and it’s made even worse in smaller settings. Avoid this by knowing ahead of time how a particular typeface looks at the intended size and medium.

Aachen Black has very small counters, and should be saved for larger display settings. The upper example looks fine, but the lower setting loses its legibility as the counters start to get smaller, and in some environments will appear to fill in.

Serifs or lack thereof: While serifs are generally believed to enhance legibility, this is not always the case. All of the above factors contribute more to legibility than the serifs: a sans serif design with neutral features can be more legible than some serif typefaces. In addition, it is believed by many professionals that what you read most, you read best. Therefore, in the U.S. where running text in books, magazines, and newspapers are typeset using serif text fonts, readers are most comfortable and familiar with reading serif fonts, and therefore can be more legible to these readers. In countries where sans serifs are more commonly used, they might appear more legible to this audience.

Keep in mind that that not all typefaces are designed to be legible. This is more of a consideration for text designs where the degree of legibility relates directly to holding the reader’s attention for the length of the copy. Display designs are generally used for a fewer words in larger sizes where the objective is to attract a reader’s eye and to convey a mood, feeling, or message, so legibility might not of primary consideration.

Readability

Readability is related to how the type is arranged, or typeset, and therefore is controlled by the designer. Factors affecting type’s readability include:

Type size: When setting text, the smaller the size, the more challenging it can be to read. This is especially true for seniors, children, and those with visual impairments. For these reasons, the demographics of your intended audience should be taken into consideration when deciding on a size for text.

Consider the demographics of your audience when selecting a type size: smaller type is harder to read for many, including seniors, children, and visually challenged individuals.

Type case: All cap settings for lengthy text are more challenging to read due to the lack of ascenders and descenders which contribute to character recognition, so stick to upper and lowercase when readability is of prime importance.

Consider the demographics of your audience when selecting a type size: smaller type is harder to read for many, including seniors, children, and visually challenged individuals.

Line spacing (aka leading): Tight line spacing impacts readability negatively. The amount needed to improve readability will depend on the size and design of a typeface as well as its x-height. Therefore, when ease of reading is of high importance, make sure there is enough line spacing to maximize readability, which in general is at least two to three points for print, and a bit more for smaller digital devices.

Tight line spacing reduces readability, as you can clearly see in this setting of Expo Serif set in 18/18 point (left) and 18/23 point (right).

Line length: When the line length, or column width, is too short, it can have many hyphenated words, which reduce readability. In addition, the eyes have to make many ‘returns’ that can cause fatigue and reduce comprehension. On the other hand, very long lines can cause confusion when shifting from the end of one line to the beginning of another. For best readability, stick to ‘average’ line length, which is usually between 45 and 70 characters.

Color, or contrast: Make sure there is enough color contrast between the type and its background, lest it becomes harder to read. This is important whether you are using black and white (and tints of the former) as well as color. When styling type for digital usage, be sure to allow for variation from one device, platform, and settings to another, as they can vary dramatically in how they display color and contrast.

High contrast between the type and the background ensure good readability.

A legible typeface such as ITC Flora can sacrifice readability when set with tight line spacing (18/18 point), while its readability improves dramatically when set smaller, but with more line spacing (16/24) point.

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Posted on: April 25, 2018

Ilene Strizver

Ilene Strizver, founder of The Type Studio, is a typographic consultant, designer, writer and educator specializing in all aspects of visual communication, from the aesthetic to the technical. Her book, Type Rules! The designer’s guide to professional typography, 4th edition, has received numerous accolades from the type and design community.

2 Comments on Legibility and Readability: What’s the Difference?

  1. Robert Marchand

    April 25, 2018 at 4:34 pm

    To bad there is no synonym for both of those words in French. A well written article revealing the fundamentals about good typography. All beginners in design should read carefully, be aware of and if I may say: follow to the letter…

  2. A very interesting article. Regarding line length, a wise and very experienced book designer once taught me that the ideal was 2.5 alphabets. With 26 letters in the standard English alphabet, that equates to 65 characters per line (in keeping with the 45-70 characters recommended above). I find this a useful rule of thumb when trying to persuade clients that their preferred design will result in lines that are either too short or too long.

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