The size-adjust CSS descriptor for the @font-face at-rule defines a multiplier for glyph outlines and metrics associated with this font. This makes it easier to harmonize the designs of various fonts when rendered at the same font size.

The size-adjust descriptor behaves in a similar fashion to the font-size-adjust property. It calculates an adjustment per font by matching ex heights.


size-adjust: 90%;



A <percentage> value with an initial value of 100%.

All metrics associated with this font are scaled by the given percentage. This includes glyph advances, baseline tables, and overrides provided by @font-face descriptors.

Formal definition

Related at-rule@font-face
Initial value100%
Percentagesas specified
Computed valueas specified

Formal syntax

size-adjust = 
<percentage [0,∞]>


Overriding metrics of a fallback font

The size-adjust property can help when overriding the metrics of a fallback font to better match those of a primary web font.

@font-face {
  font-family: web-font;
  src: url("");

@font-face {
  font-family: local-font;
  src: local(Local Font);
  size-adjust: 90%;


CSS Fonts Module Level 5
# size-adjust-desc

Browser compatibility

BCD tables only load in the browser

See also