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.

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 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

<line-width>

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

Examples

Setting an element's outline width

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;
}

Result

Specifications

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

Browser compatibility

BCD tables only load in the browser

See also