outline-width

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.

Try it

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

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;

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 definition

Initial valuemedium
Applies toall elements
Inheritedno
Computed valuean absolute length; if the keyword none is specified, the computed value is 0
Animation typea length

Formal syntax

outline-width = 
  <line-width>  

<line-width> = 
  <length [0,∞]>  |
  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;
}

Result

Specifications

Specification
CSS Basic User Interface Module Level 4
# outline-width

Browser compatibility

BCD tables only load in the browser

See also