OpenType

OpenType is a font format that supports advanced typographic features including ligatures, small caps, old-style figures, and alternate characters. These features are accessed in CSS via the font-feature-settings property. Not all fonts ship the same features; a font must include the relevant glyphs to expose the feature. The font inspector shows which OpenType features a specific font file supports. Test them live in the typography playground.

Enabling features globally without testing. Some OpenType features like ligatures and old-style figures are meant for specific contexts. Enabling them in UI elements like buttons or labels can produce unexpected character substitutions.

Not checking feature availability. A font must include the relevant glyphs to expose an OpenType feature. Assuming a font has small caps when it does not produces missing character glyphs rather than the intended effect.

OpenType is the wrapper that lets one font file carry advanced behavior: standard and discretionary ligatures, small caps, old-style figures, fractions, and alternate letterforms. The ones a layout reaches for most are small caps for acronym styling and old-style figures for text that should read like prose numerals. Both are accessed in CSS through font-feature-settings or the friendlier font-variant-* properties, and support is reliable in current browsers.

The catch is that features are optional: a font only exposes them if the designer drew and shipped the glyphs. Before promising users small caps or contextual alternates, confirm the family ships them, then test on the actual browser. The font inspector lists the features a loaded family exposes, which turns a vague hope into a concrete CSS line for the stylesheet.