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outline

The CSS outline property is a shorthand property for setting one or more of the individual outline properties outline-style, outline-width and outline-color in a single declaration. In most cases the use of this shortcut is preferable and more convenient.

Outlines differ from borders in the following ways:

  • Outlines do not take up space, they are drawn above the content.
  • Outlines may be non-rectangular. They are rectangular in Gecko/Firefox. But e.g. Opera draws a non-rectangular shape around a construct like this:
    TEXTTEXTTEXT
Initial value as each of the properties of the shorthand:
Applies to all elements
Inherited no
Media visual, interactive
Computed value as each of the properties of the shorthand:
  • outline-color: For the keyword invert, the computed value is invert. For the color value, if the value is translucent, the computed value will be the rgba() corresponding one. If it isn't, it will be the rgb() corresponding one. The transparent keyword maps to rgb(0,0,0).
  • outline-width: an absolute length; if the keyword none is specified, the computed value is 0
  • outline-style: as specified
Animation type as each of the properties of the shorthand:
Canonical order order of appearance in the formal grammar of the values

Syntax

/* width | style | color */
outline: 1px solid white;

/* Global values */
outline: inherit;
outline: initial;
outline: unset;

Values

One, two or three values, given in arbitrary order:

<'outline-width'>
See outline-width.
<'outline-style'>
See outline-style.
<'outline-color'>
Since Gecko 1.9 (Firefox 3), the value of the element's color property (foreground color) is used. See outline-color.

Formal syntax

[ <'outline-color'> || <'outline-style'> || <'outline-width'> ]

Examples

outline: solid; | outline: dashed red; | outline: dotted 1px; | outline: ridge thick violet; | outline: custom 5px;

/* two identical declarations */

:link:hover { outline: 1px solid #000; }
:link:hover { outline: solid black 1px; }

Specifications

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

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1.0 (Yes) 1.5 (1.8)[1] 8.0 7.0 1.2 (125)
Feature Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 1.0 (Yes) 1.0 (1.8) [1] 8.0 6.0 3.1

[1] In browsers previous to Gecko 1.8 (Firefox 1.5) a similar effect can be achieved using Mozilla CSS Extension -moz-outline.

Firefox includes absolutely positioned elements inside the outline (bug 687311).

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https://developer.mozilla.org/en-US/docs/Web/CSS/outline