`outline-width` CSS property

Baseline

Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

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The CSS outline-width 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.

Try it

outline-width: 12px;

outline-width: thin;

outline-width: medium;

outline-width: thick;

<section class="default-example" id="default-example">
  <div class="transition-all" id="example-element">
    This is a box with an outline around it.
  </div>
</section>

#example-element {
  outline: 0.75em solid;
  padding: 0.75em;
  width: 80%;
  height: 100px;
}

Syntax

css

/* 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;
outline-width: initial;
outline-width: revert;
outline-width: revert-layer;
outline-width: unset;

Values

This property is specified as one <line-width> value.

<line-width>: Defines the width of the outline, either as an explicit non-negative <length> or the keywords: thin, medium, or thick. The default is medium.

Formal definition

Initial value	`medium`
Applies to	all elements
Inherited	no
Computed value	the absolute `<length>`, snapped as a line width
Animation type	a length

Formal syntax

outline-width = 
  <line-width>  

<line-width> = 
  <length [0,∞]>  |
  hairline        |
  thin            |
  medium          |
  thick

Examples

Setting an element's outline width

HTML

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

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;
}