Web/CSS/font-optical-sizing

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

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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: 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

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	Status	Comment
CSS Fonts Module Level 4The definition of 'font-optical-sizing' in that specification.	Working Draft

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
font-optical-sizing	Chrome Full support 79	Edge Full support 17	Firefox Full support 62 Full support 62 No support 60 — 62 Disabled' Disabled' From version 60 until version 62 (exclusive): this feature is behind the layout.css.font-variations.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 66	Safari Full support 11	WebView Android Full support 79	Chrome Android Full support 79	Firefox Android Full support 62 Full support 62 No support 60 — 62 Disabled' Disabled' From version 60 until version 62 (exclusive): this feature is behind the layout.css.font-variations.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS Full support 11	Samsung Internet Android Full support 12.0

Legend

Full support  

Full support

No support  

No support

User must explicitly enable this feature.'

User must explicitly enable this feature.

font-optical-sizing by Mozilla Contributors is licensed under CC-BY-SA 2.5.