outline-width - CSS: Cascading Style Sheets 编辑

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.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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 value	medium
Applies to	all elements
Inherited	no
Computed value	an absolute length; if the keyword none is specified, the computed value is 0
Animation type	a 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

• outline
• outline-color
• outline-style