outline

The outline CSS shorthand property sets the style, color, and width of an element’s outline.

The outline shorthand property sets the style, color, and width of an element’s outline. It can be specified using one, two, or three values. The order of the values does not matter. Any omitted sub-values are set to their initial value.

The outline will be invisible for many elements if its style is not defined. This is because the style defaults to none. A notable exception is input elements, which are given default styling by browsers.

Outline is a line outside of the element’s border. Unlike other areas of the box, outlines don’t take up space, so they don’t affect the layout of the document in any way.

Syntax example: outline: solid;