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The border-width property is a shorthand property for setting border-top-widthborder-right-widthborder-bottom-width and border-left-width of a box at the same place.

/* border-width: width */ /* the width applies to all sides */
border-width: 5px;

/*border-width: top&bottom right&left */
border-width: 2px 1.5em;

/* border-width: top right&left bottom */
border-width: 1px 2em 1.5cm;

/* border-width: top right bottom left */
border-width: 1px 2em 0 4rem;

border-width: inherit;

Initial valueas each of the properties of the shorthand:
Applies toall elements. It also applies to ::first-letter.
Computed valueas each of the properties of the shorthand:
Animation typeas each of the properties of the shorthand:
Canonical orderthe unique non-ambiguous order defined by the formal grammar



Is either a non-negative explicit <length> value or a keyword denoting the thickness of the border area of a box. The keyword must be one of the following values:
A thin border
A medium border
A thick border
The specification doesn't precisely define the thickness of each of the keywords, which is therefore implementation specific. Nevertheless, it requests that the thickness does follow the thin ≤ medium ≤ thick inequality and that the values are constant on a single document.
Is a keyword indicating that all four values are inherited from their parent's element calculated value.

Formal syntax


<br-width> = <length> | thin | medium | thick


A mix of values and lengths


<p id="sval">
    one value: 6px wide border on all 4 sides</p>
<p id="bival">
    two different values: 2px wide top and bottom border, 10px wide right and left border</p>
<p id="treval">
    three different values: 0.3em top, 9px bottom, and zero width right and left</p>
<p id="fourval">
    four different values: "thin" top, "medium" right, "thick" bottom, and 1em right</p>


#sval {
    border: ridge #ccc;
    border-width: 6px;
#bival {
    border: solid red;
    border-width: 2px 10px;
#treval {
    border: dotted orange;
    border-width: 0.3em 0 9px;
#fourval {
    border: solid lightgreen;
    border-width: thin medium thick 1em;
p {
    width: auto;
    margin: 0.25em;
    padding: 0.25em;



Specification Status Comment
CSS Backgrounds and Borders Module Level 3
The definition of 'border-width' in that specification.
Candidate Recommendation No direct change, the <length> CSS data type extension has an effect on this property.
CSS Level 2 (Revision 1)
The definition of 'border-width' in that specification.
Recommendation Added the constraint that values' meaning must be constant inside a document.
CSS Level 1
The definition of 'border-width' in that specification.
Recommendation Initial definition

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 1.0 (Yes) 1.0 (1.7 or earlier) 4.0 3.5 1.0 (85)
Feature Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 2.0 (Yes) 1.0 (1.9.2) 6.0 11 3.0

See also