An outline is a line drawn outside the element's border.
An outline is a line that is drawn around elements, OUTSIDE the borders, to make the element "stand out".
CSS has the following outline properties:
outline-styleoutline-coloroutline-widthoutline-offsetoutlineNote: Outline differs from borders! Unlike border, the outline is drawn outside the element's border, and may overlap other content. Also, the outline is NOT a part of the element's dimensions; the element's total width and height is not affected by the width of the outline.
The outline-style property specifies the style of the outline, and can have one of the following values:
dotted - Defines a dotted outlinedashed - Defines a dashed outlinesolid - Defines a solid outlinedouble - Defines a double outlinegroove - Defines a 3D grooved outlineridge - Defines a 3D ridged outlineinset - Defines a 3D inset outlineoutset - Defines a 3D outset outlinenone - Defines no outlinehidden - Defines a hidden outlineThe following example shows the different outline-style values:
Demonstration of the different outline styles: