Distance from border to outline
outline-offset
Specify the distance from the element's outline ("outside-the-box") border to its normal border.
Property values
This property sets the distance to offset the outline from the element's normal border. Positive offsets place it outside the border. Negative values place it inside the border.
Unlike many other similar properties, the outline-offset property does not have corresponding top, right, bottom and left properties. Outline-offset rules can only be set for all four sides at once.
Use any of these font-relative typographic units to set the outline offset:
| em | em | The font-size of the current font |
| rem | relative em | The font-size of the <html> element |
| lh | line height | The line-height of the current font |
| rlh | relative line height | The line-height of the <html> element |
| cap | cap height | The nominal height of the current font's capital letters |
| ex | "x" | The height of the current font's "x" glyph |
| ch | "0" | The advance measure (the width) of the current font's "0" glyph |
| ic | ideograph count | The advance measure (the width) of the current font's "水" ideograph |
Or use any of these fixed size units which are independent of the current font:
| in | inch | A size equal 96px |
| px | pixels | A size equal to 1/96 inch |
| pt | point | A size equal 1in/72 = 1.33px |
| pc | pica | A size equal 1in/6 = 12pt = 16px |
| cm | centimeter | A size equal to 96px/2.54 = 37.8px |
| mm | millimeter | A size equal to 96px/25.4 = 3.8px |
| Q | quarter millimeter | A size equal to 96px/1016 = 0.94px |
Examples
/* an outline drawn outside the element's normal border */
outline-offset: 2px;
/* an outline drawn inside the element's normal border */
outline-offset: -2px;