Readability Do's and Don'ts

This article was written in 1990 as a guide for desktop print publishing. All of the rules listed are applicable to Web publishing, and in most cases, are even more important on the Web.

With the advent of personal computer word processing, we all became typographers. Good typography is readable. In this context, readability does not refer to the quality of the writing, but to the relative ease with which the reader can translate an abstract set of shapes—letters, words and paragraphs—into meaningful symbols.

Sentence spacing

Some of us still put two spaces between sentences, which is a holdover from the days of the typewriter. We are not using typewriters now. Use only one space between sentences and one space after colons and other punctuation.

On the Web, never use multiple non-breaking spaces <&nbsp;> to add space or to attempt to align columns of type.

Alignment

Flush left, also called "ragged right," is the most readable alignment. It provides uniform or normal letter and word spacing, minimizes awkward hyphenation of words and provides the eye with a common starting point for each line. Any significant amount of text set centered or ragged left is very difficult to read because the eye must search for the start of each new line.

Justified alignment—flush left and right—compresses or expands letter and word spacing to fit a given line and can produce awkward hyphenation of words. The disadvantages of justified text can be reduced by increasing the line length or by decreasing the point size of the type, but that also may reduce readability.

On the Web, flush left is the universal standard.

Line length

Line length is very important to readability, especially for justified alignment. As a general guide, line length should be between 1.5 and two times the lowercase alphabet in the type and point size being used. If the line is too long, it is difficult for the eye to accurately and quickly locate the start of the next line. If the line is too short, especially with justified alignment, excessive hyphenation and exaggerated letter and word spacing renders text visually unattractive and virtually unreadable.

On the Web, it's important to keep columns relatively narrow for several reasons, most especially with the growing audience on mobile devices. If long lines make it difficult for the eye to accurately and quickly locate the start of the next line in print—or on a full-size monitor—imagine how much fun it is if the reader has to scroll back and forth on every line.   

Line spacing

The original method of type composition was hand-set cold metal type. Line spacing is called "leading" because in hand-set metal type, line spacing was increased by inserting thin strips of metal between the lines of type. In general, increasing the leading (line spacing) increases the readability.

On the Web, line spacing can be increased using style sheets, but the more important factor for readability is line length.

ALL CAPS

Perhaps the most frequently violated rule of readability involves the use of ALL CAPS (capital letters). Designers are often drawn to all caps because it forms neat, uniform, visual elements, or "blocks." Unfortunately, for precisely that reason, type set in all caps is more difficult to read.

Your brain does not recognize words solely on the basis of specific letter combinations, but on the overall shape of the words. In fact, your brain recognizes whole phrases based on letter shape rather than identifying individual letters and words. Which of the following is easier to read: GOOD OLD DOG or good old dog?

For readability, avoid all caps even in heads and subheads. The most readable headlines and subheads are set with only the first letter of the first word and proper nouns capitalized, just as in sentences.

On the Web, all caps are even harder to read than in print. Everything is harder to read on the Web, which is why placing readability above graphic design is paramount to effective Web communication.

Type face selection

Sans serif type faces are neither more nor less readable than serif type faces. Readability is enhanced by selecting common type faces, such as Helvetica, Times, Garamond and Univers, to name just a few. Common type faces have become common type faces because of their versatility and readability. And, because they are common, their letter shapes are immediately recognizable to most readers.

On the Web, there are a handful of fonts, mostly sans serif, that are used universally. They include Arial, Helvetica, Univers and Verdana.

Thom Myers
Western Michigan University