font-size-adjust CSS property sets the size of lower-case letters relative to the current font size (which defines the size of upper-case letters).
/* Use the specified font size */ font-size-adjust: none; /* Use a font size that makes lowercase letters half the specified font size */ font-size-adjust: 0.5; /* Two values - added in the Level 5 spec */ font-size-adjust: ex-height 0.5; /* Global values */ font-size-adjust: inherit; font-size-adjust: initial; font-size-adjust: revert; font-size-adjust: revert-layer; font-size-adjust: unset;
The property is useful since the legibility of fonts, especially at small sizes, is determined more by the size of lowercase letters than by the size of capital letters. Legibility can become an issue when the first-choice
font-family is unavailable and its replacement has a significantly different aspect ratio (the ratio of the size of lowercase letters to the size of the font).
To use this property in a way that is compatible with browsers that do not support
font-size-adjust, it is specified as a number that the
font-size property is multiplied by. This means the value specified for the property should generally be the aspect ratio of the first choice font. For example, consider this style sheet:
font-size: 14px; font-size-adjust: 0.5;
It is really specifying that the lowercase letters of the font should be
7px high (0.5 × 14px). This will still produce reasonable results in browsers that do not support
font-size-adjust, where a
14px font will be used.