OpenType is an extension of the TrueType computer font format. The format is cross-platform (meaning the same font can be used on Windows, Apple, and other machines), and is based on the Unicode character set. This allows a single font file to contain glyphs for several different languages and writing systems.

A major addition is native support for advanced typography. The features available in any particular font will depend on which ones the font designer included. The following introduces some of the new capabilities.

Swash

Swashes add an old-style flair to certain terminal letters.

Ligatures

Some letter combinations look better when joined in special ways. OpenType supports automatic substitution for such sequences.

Normal text without ligatures. The i-dots are crowded by the f's overhang. The text definitely looks computer generated, not organic.		The same text with ligatures turned on. The T-h, f-i, and f-f-i series of letters are automatically joined for a cleaner look. The T's serif is merged with the h's vertical stem, the i-dots are absorbed by the f's tip, and the consecutive f's are joined in a more attractive way.

Discretionary Ligatures

Additional ligatures are supported for adding a caligraphic feel to the letter forms.

Small Caps

Special, small forms of capital letters are used for titles and emphasis. The small letter forms retain the same stroke weight of the larger characters. The conventional method for making small caps—using regular capitals in a smaller font size—leads to letter forms that are thinner and less appealing.

Faux small caps. Notice how the strokes of the small caps are narrower than those of the full capitals.		OpenType small caps. Weight looks more consistent, like letters were written with the same pen nib.

A full-sized capital M.

A small-cap M enlarged to the same size as the capital M for comparison.

Ordinals and Fractions

Ordinals and fraction sequences are automatically substituted with the proper superscripted and subscripted letterforms. Special small letter forms are used so that the font weight is kept consistent.

is automatically turned into

Numeral Styles

Numerals can be shown in either lining or old-style. Lining numerals are the default in most fonts and applications, however old-style numerals tend to look better in prose, fitting in better with surrounding lowercase text. Old-style numerals can be thought of as "lower case" numbers.

Lining numerals

Old-style numerals

Numerals' widths can also be altered to either proportional or tabular. Proportional mode makes each digit only as wide as is necessary, while tabular mode ensures each digit is of equal width (so that all the digits in a table line up evenly, hence the name tabular).

Proportional numerals. Ones are narrower than eights.

Tabular numerals. All digits line up, regardless of actual letterform width.

Superscripts and Subscripts

OpenType supports alternate small letterforms for superscript and subscript characters. Again, the letterforms match the weight of the larger forms for a consistent look.

Other Features

OpenType also supports more variations than just bold and italic. Some fonts may have many different weights, title versions versus text versions, or choice of oblique angles.

Variations in stroke weight.

For those wanting ultimate control over the look of text, individual letters and letter sequences can be subsituted with alternates, when available. Any character can have a number of different letterforms stored in the same font. This is especially useful for adding nuances to handwriting-based fonts.

Individual glyph variations

Substituting a capital letter with a larger, more ornate swash version.