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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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No No


33 — 341

No No9
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support No No No34 No No9.1

1. From version 33 until version 34 (exclusive): this feature is behind the layout.css.font-features.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

Document Tags and Contributors

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