font-size-adjust

The font-size-adjust CSS property adjusts the size of a font to match a chosen font metric, such as the height of lowercase letters, to a specified proportion of the font-size. This property is intended for adjusting fallback fonts to have similar metrics as the first-choice font.

Legibility can become an issue when the first-choice font-family is unavailable and its replacement fallback font has a significantly different aspect value (height of lowercase letters divided by font size). Legibility of fonts, especially at small font sizes, is determined more by the size of lowercase letters than by the size of uppercase letters. The font-size-adjust property is useful for adjusting the font size of fallback fonts to keep the aspect value across fonts consistent, ensuring that the text appears similar regardless of the font used.

Syntax example: font-size-adjust: none;