`font-synthesis-weight` CSS property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It's been available across browsers since March 2023.

The font-synthesis-weight CSS property lets you specify whether or not the browser may synthesize the bold typeface when it is missing in a font family.

It is often convenient to use the shorthand property font-synthesis to control all typeface synthesis values.

Syntax

/* Keyword values */
font-synthesis-weight: auto;
font-synthesis-weight: none;

/* Global values */
font-synthesis-weight: inherit;
font-synthesis-weight: initial;
font-synthesis-weight: revert;
font-synthesis-weight: revert-layer;
font-synthesis-weight: unset;

Values

This property is specified as one of the following keyword values:

auto: Indicates that the missing bold typeface may be synthesized by the browser if needed.
none: Indicates that the synthesis of the missing bold typeface by the browser is not allowed.

Formal definition

Initial value	auto
Applies to	all elements and text
Inherited	yes
Computed value	as specified
Animation type	discrete

Formal syntax

font-synthesis-weight = 
  auto |
  none

Examples

Disabling synthesis of bold typeface

This example shows turning off synthesis of the bold typeface by the browser in the Montserrat font.

HTML

<p class="english">
  This is the default <strong>bold typeface</strong> and
  <em>oblique typeface</em>.
</p>

<p class="english no-syn">
  The <strong>bold typeface</strong> is turned off here but not the
  <em>oblique typeface</em>.
</p>

CSS

@import "https://fonts.googleapis.com/css2?family=Montserrat&display=swap";

.english {
  font-family: "Montserrat", sans-serif;
}
.no-syn {
  font-synthesis-weight: none;
}

Result

Specifications

Specification
CSS Fonts Module Level 4 # font-synthesis-weight

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`font-synthesis-weight`	97	97	111	83	16.4	97	111	68	16.4	18.0	97	16.4
`auto`	97	97	111	83	16.4	97	111	68	16.4	18.0	97	16.4
`none`	97	97	111	83	16.4	97	111	68	16.4	18.0	97	16.4