font-synthesis

The font-synthesis CSS property controls which missing typefaces, bold or italic, may be synthesized by the browser.

font-synthesis: none;
font-synthesis: weight;
font-synthesis: style;
font-synthesis: weight style;
/* Global values */
font-synthesis: initial;
font-synthesis: inherit;
font-synthesis: unset;

Most standard Western fonts include italic and bold variants, but many novelty fonts do not. Fonts used for Chinese, Japanese, Korean and other logographic scripts tend not to include these variants, and synthesizing them may impede the legibility of the text. In these cases, it may be desirable to switch off the browser's default font-synthesis.

Syntax

This property can take any one of the following forms:

• the keyword value none
• either of the keyword values weight and style
• both the keyword values weight and style.

Values

none

This keyword indicates that neither bold nor italic typeface may be synthesized.

weight

This keyword indicates that a bold typeface may be synthesized if needed.

style

This keyword indicates that an italic typeface may be synthesized if needed.

Formal syntax

none | [ weight || style ]

Examples

HTML

<em class="syn">Synthesize me! 站直。</em>
<br/>
<em class="no-syn">Don't synthesize me! 站直。</em>

CSS

em {
  font-weight: bold;
}
.syn {
  font-synthesis: style weight;
}
.no-syn {
  font-synthesis: none;
}

Result

Specifications

Browser Compatibility

[1] Experimental implementation was available since Gecko 33. It was governed by the preference layout.css.font-features.enabled defaulting to true on Nightly and Aurora only.