In typography, text or font in all caps (short for "all capitals") contains capital letters without any lowercase letters. For example: THIS TEXT IS IN ALL CAPS. All-caps text can be seen in legal documents, advertisements, newspaper headlines, and the titles on book covers. Short strings of words in capital letters appear bolder and "louder" than mixed case, and this is sometimes referred to as "screaming" or "shouting". All caps can also be used to indicate that a given word is an acronym.
Studies have been conducted on the readability and legibility of all caps text. Scientific testing from the 20th century onward has generally indicated that all caps text is less legible and readable than lower-case text. In addition, switching to all caps may make text appear hectoring and obnoxious for cultural reasons, since all-capitals is often used in transcribed speech to indicate that the speaker is shouting. All-caps text is common in comic books, as well as on older teleprinter and radio transmission systems, which often do not indicate letter case at all.
In professional documents, a commonly preferred alternative to all caps text is the use of small caps to emphasise key names or acronyms (for example, ), or the use of italics or (more rarely) bold. In addition, if all caps must be used it is customary to slightly widen the spacing between the letters, by around 10 per cent of the point height. This practice is known as tracking or letterspacing. Some digital fonts contain alternative spacing metrics for this purpose.
Association with shouting or yelling
Messages typed completely in capital letters are often equated on social media to shouting and other impolite or argumentative behaviors. This became a mainstream interpretation with the advent of networked computers, from the 1980s onward. However, a similar interpretation was already evidenced by written sources that predated the computing era, in some cases by at least a century, and the textual display of shouting or emphasis was still not a settled matter by 1984. The following sources may be relevant to the history of all caps: The 17 April 1856 edition of the Yorkville Enquirer (South Carolina) uses the expression "This time he shouted it out in capital letters." The 1880 book The Standard speaker and elocutionist has a section titled "SHOUTING STYLE", which states that "This will be seldom needed throughout an entire piece, but wherever the words imply calling, or commanding, it will be in keeping with the words to employ it. As examples note the following selections marked in CAPITAL letters as the appropriate place for shouting emphasis." A large number of literature examples are then given where all caps has been used to represent shouting. The 6 September 1958 edition of Bookseller: The Organ of the Book Trade describes writing in lower-case "rather than shouting with all caps. The effect is pleasing to anybody in a contemplative mood." A 2014 article on netiquette (online etiquette) in New Republic, titled "How Capital Letters Became Internet Code for Yelling", states that: According to Professor Paul Luna (of the University of Reading's department of typography and graphic communication), all caps has been used "to convey grandeur, pomposity, or aesthetic seriousness for thousands of years", and for many years to express anger or shouting in print. Examples are cited such as pianist Philippa Schuyler's 1940s biography titled "Composition in Black and White", which used all-caps to "yell", and Robert Moses, who in the 1970s used all caps to "convey rage" at a draft of a book. Online newsgroups and bulletin board posts from around 1984 show that a user still needed to explain that "if it's in caps i'm trying to YELL", or that "Capitalizing whole words gives the impression that you're shouting". Another summed up that there seemed to be a developing consensus that emphasis was given to words via all caps, or by surrounding them with asterisks.
Usage
Print media
Before the development of lower-case letters in the 8th century, texts in the Latin alphabet were written in a single case, which is now considered to be capital letters. Text in all caps is not widely used in body copy. The major exception to this is the so-called fine print in legal documents.