Web/CSS/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.

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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 3The 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

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`outline-width`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1.5 Full support 1.5 No support 1 — 3.6 Prefixed' Prefixed' Implemented with the vendor prefix: -moz-	IE Full support 8	Opera Full support 7	Safari Full support 1.2	WebView Android Full support 37	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 14	Safari iOS Full support 1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support
Requires a vendor prefix or different name for use.': Requires a vendor prefix or different name for use.

outline-width by Mozilla Contributors is licensed under CC-BY-SA 2.5.