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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.

Initial valueweight style
Applies toall elements. It also applies to ::first-letter and ::first-line.
Computed valueas specified
Animation typediscrete
Canonical orderorder of appearance in the formal grammar of the values


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.


This keyword indicates that neither bold nor italic typeface may be synthesized.
This keyword indicates that a bold typeface may be synthesized if needed.
This keyword indicates that an italic typeface may be synthesized if needed.

Formal syntax

none | [ weight || style ]



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


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



Specification Status Comment
CSS Fonts Module Level 3
The definition of 'font-synthesis' in that specification.
Candidate Recommendation Initial definition

Browser Compatibility

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari (WebKit)
Basic support 34 (34) [1] ? ? ? 10.0
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? 34.0 (34)[1] ? ? ?

[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.

Document Tags and Contributors

 Contributors to this page: wbamberg, y6nH, clagnut, duncanmcdonald, Sebastianz, fscholz, xfq, teoli
 Last updated by: wbamberg,