Typesetting is the composition of text by means of arranging physical type (or sort) in mechanical systems or glyphs in digital systems representing characters (letters and other symbols). Stored types are retrieved and ordered according to a language's orthography for visual display. Typesetting requires one or more fonts (which are widely but erroneously confused with and substituted for typefaces). One significant effect of typesetting was that authorship of works could be spotted more easily, making it difficult for copiers who have not gained permission.

Pre-digital era

Manual typesetting

During much of the letterpress era, movable type was composed by hand for each page by workers called compositors. A tray with many dividers, called a case, contained cast metal sorts, each with a single letter or symbol, but backwards (so they would print correctly). The compositor assembled these sorts into words, then lines, then pages of text, which were then bound tightly together by a frame, making up a form or page. If done correctly, all letters were of the same height, and a flat surface of type was created. The form was placed in a press and inked, and then printed (an impression made) on paper. Metal type read backwards, from right to left, and a key skill of the compositor was their ability to read this backwards text.

Before computers were invented, font sizes were changed by physically adjusting the size of the letterpress type, or by using a different size of type. In letterpress printing, individual letters and punctuation marks were cast on small metal blocks, known as "sorts," and then arranged to form the text for a page. The size of the type was determined by the height of the sort, and a printer would need to physically swap out the sorts for a different size to change the font size.

During typesetting, individual sorts are picked from a type case with the right hand, and set into a composing stick held in the left hand from left to right, and as viewed by the setter upside down. As seen in the photo of the composing stick, a lower case 'q' looks like a 'd', a lower case 'b' looks like a 'p', a lower case 'p' looks like a 'b' and a lower case 'd' looks like a 'q'. This is reputed to be the origin of the expression "mind your p's and q's". It might just as easily have been "mind your b's and d's".

A forgotten but important part of the process took place after the printing: the expensive sorts had to be sorted, so they would be ready for reuse. Errors in sorting would produce later misprints.

The diagram at right illustrates a cast metal sort: a face, b body or shank, c point size, 1 shoulder, 2 nick, 3 groove, 4 foot. Wooden printing sorts were used for centuries in combination with metal type. Not shown, and more the concern of the casterman, is the “set”, or width of each sort. Set width, like body size, is measured in points.

In order to extend the working life of type, and to account for the finite sorts in a case of type, copies of forms were cast when anticipating subsequent printings of a text, freeing the costly type for other work. This was particularly prevalent in book and newspaper work where rotary presses required type forms to wrap an impression cylinder rather than set in the bed of a press. In this process, called stereotyping, the entire form is pressed into a fine matrix such as plaster of Paris or papier mâché to create a flong, from which a positive form is cast in type metal.

Advances such as the typewriter and computer would push the state of the art even farther ahead. Still, hand composition and letterpress printing have not fallen completely out of use, and since the introduction of digital typesetting, it has seen a revival as an artisanal pursuit. However, it is a small niche within the larger typesetting market.