The outline-width CSS property sets the width (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.

/* 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;

Initial valuemedium
Applies toall elements
Inheritedno
Mediavisual, interactive
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

Syntax

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

Values

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

Formal syntax

<br-width>

where
<br-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.
Candidate 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.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1.0 (Yes) 1.5 (1.8)[1] 8.0 7.0 1.2 (125)
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? (Yes) ? ? ? ?

[1] In browsers previous to Gecko 1.8 (Firefox 1.5) essentially the same effect can be achieved using Mozilla CSS Extension -moz-outline-width.

Document Tags and Contributors

 Last updated by: mfluehr,