outline

The outline CSS property is a shorthand to set various outline properties in a single declaration: outline-style, outline-width, and outline-color.

As with all shorthand properties, any omitted sub-values will be set to their initial value.

Borders vs. outlines

Borders and outlines are very similar. However, outlines differ from borders in the following ways:

• Outlines never take up space, as they are drawn outside of an element's content.
• According to the spec, outlines don't have to be rectangular, although they usually are.

Syntax

/* style */
outline: solid;

/* color | style */
outline: #f66 dashed;

/* style | width */
outline: inset thick;

/* color | style | width */
outline: green solid 3px;

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

The outline property may be specified using one, two, or three of the values listed below. The order of the values does not matter.

Values

<'outline-color'>

Sets the color of the outline. Defaults to currentcolor if absent. See outline-color.

<'outline-style'>

Sets the style of the outline. Defaults to none if absent. See outline-style.

<'outline-width'>

Sets the thickness of the outline. Defaults to medium if absent. See outline-width.

Formal syntax

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

Example

HTML

<a href="#">This link has a special focus style.</a>

CSS

a {
  border: 1px solid;
  border-radius: 3px;
  display: inline-block;
  margin: 10px;
  padding: 5px;
}

a:focus {
  outline: 4px dotted #e73;
  outline-offset: 4px;
  background: #ffa;
}

Result

Accessibility concerns

Assigning outline a value of 0 or none will remove the browser's default focus style. If an element can be interacted with, it must have a visible focus indicator. Provide obvious focus styling if the default focus style is removed.

• :focus — CSS | MDN
• How to Design Useful and Usable Focus Indicators

• Understanding Success Criterion 2.4.7 | Understanding WCAG 2.0

Specifications

Browser compatibilityUpdate compatibility data on GitHub