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font-optical-sizing

The font-optical-sizing CSS property sets whether text rendering is optimized for viewing at different sizes.

Try it

Syntax

/* keyword values */
font-optical-sizing: none;
font-optical-sizing: auto; /* default */

/* Global values */
font-optical-sizing: inherit;
font-optical-sizing: initial;
font-optical-sizing: revert;
font-optical-sizing: revert-layer;
font-optical-sizing: unset;

Values

none: The browser will not modify the shape of glyphs for optimal viewing.
auto: The browser will modify the shape of glyphs for optimal viewing.

Description

Optical sizing is enabled by default for fonts that have an optical size variation axis. The optical size variation axis is represented by opsz in font-variation-settings.

When optical sizing is used, small text sizes are often rendered with thicker strokes and larger serifs, whereas larger text is often rendered more delicately with more contrast between thicker and thinner strokes.

Formal definition

Initial value	`auto`
Applies to	all elements. It also applies to `::first-letter` and `::first-line`.
Inherited	yes
Computed value	as specified
Animation type	discrete

Formal syntax

font-optical-sizing = 
  auto  |
  none

Examples

Disabling optical sizing

<p class="optical-sizing">
  This paragraph is optically sized. This is the default across browsers.
</p>

<p class="no-optical-sizing">
  This paragraph is not optically sized. You should see a difference in
  supporting browsers.
</p>

@font-face {
  src: url("AmstelvarAlpha-VF.ttf");
  font-family: "Amstelvar";
  font-style: normal;
}

p {
  font-size: 36px;
  font-family: Amstelvar;
}

.no-optical-sizing {
  font-optical-sizing: none;
}

Note: The font referenced above — which includes optical sizing and is freely-licensed — is good for testing. You can download it on GitHub.

Specifications

Specification
CSS Fonts Module Level 4 # font-optical-sizing-def

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`font-optical-sizing`	79	17	62	No	66	11	79	79	62	No	11	12.0