box-sizing
Sets how the total width and height of an element is calculated. border-box includes padding and border in the size, while content-box does not.
It is documented as part of the CSS Box Sizing specification.
Syntax
/* Usage Example */
* {
box-sizing: border-box;
/* best practice: include padding/border in width/height */
}
/* Syntax */
box-sizing: content-box;
box-sizing: border-box;
/* Global values */
box-sizing: inherit;
box-sizing: initial;
box-sizing: revert;
box-sizing: revert-layer;
box-sizing: unset;box-sizing Browser support
Widely available
Since
2015 96% global usage
This feature is well established and works across many devices and browser versions. It has been available across browsers since 2015.
10+
29+
5.1+
12+
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