The outline-width CSS property sets the thickness of an element's outline. An outline is a line that is drawn around an element, outside the border.

It is often more convenient to use the shorthand property outline when defining the appearance of an outline.

Syntax

/* Keyword values */
outline-width: thin;
outline-width: medium;
outline-width: thick;

/* <length> values */
outline-width: 1px;
outline-width: 0.1em;

/* Global values */
outline-width: inherit;

The outline-width property is specified as any one of the values listed below.

Values

<length>
The width of the outline specified as a <length>.
thin
Depends on the user agent. Typically equivalent to 1px in desktop browsers (including Firefox).
medium
Depends on the user agent. Typically equivalent to 3px in desktop browsers (including Firefox).
thick
Depends on the user agent. Typically equivalent to 5px in desktop browsers (including Firefox).

Formal syntax

<line-width>

where
<line-width> = <length> | thin | medium | thick

Examples

HTML

<span id="thin">thin</span>
<span id="medium">medium</span>
<span id="thick">thick</span>
<span id="twopixels">2px</span>
<span id="oneex">1ex</span>
<span id="em">1.2em</span>

CSS

span {
  outline-style: solid;
  display: inline-block;
  margin: 20px;
}

#thin {
  outline-width: thin;
}

#medium {
  outline-width: medium;
}

#thick {
  outline-width: thick;
}

#twopixels {
  outline-width: 2px;
}

#oneex {
  outline-width: 1ex;
}

#em {
  outline-width: 1.2em;
}

Specifications

Specification Status Comment
CSS Basic User Interface Module Level 3
The definition of 'outline-width' in that specification.
Recommendation No change.
CSS Transitions
The definition of 'outline-width' in that specification.
Working Draft Defines outline-width as animatable.
CSS Level 2 (Revision 1)
The definition of 'outline-width' in that specification.
Recommendation Initial definition.

Initial valuemedium
Applies toall elements
Inheritedno
Mediaas each of the properties of the shorthand:
Computed valuean absolute length; if the keyword none is specified, the computed value is 0
Animation typea length
Canonical orderthe unique non-ambiguous order defined by the formal grammar

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 1Edge Full support 12Firefox Full support 1.5
Full support 1.5
No support 1 — 3.6
Prefixed
Prefixed Requires the vendor prefix: -moz-
IE Full support 8Opera Full support 7Safari Full support 1.2WebView Android ? Chrome Android ? Edge Mobile Full support YesFirefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown
Requires a vendor prefix or different name for use.
Requires a vendor prefix or different name for use.

Document Tags and Contributors

Last updated by: ddbeck,