border-block-start-width
Defines the thickness of the logical 'start' border. It replaces 'border-top-width' in modern CSS to better support different writing directions.
Quick example
header {
/* Logical top border */
border-block-start-width: 2px;
border-block-start-style: solid;
border-block-start-color: #333;
}Quick facts
Initial value
mediumInherited
No
Applies to
all elements
Animation type
byComputedValueType
Values
border-top-width border-block-start-width Browser Support
Widely available Since 2021 95% global usage
This feature is well established and works across many devices and browser versions. It has been available across browsers since 2021.
Safe to use without fallbacks.
69+
41+
12.1+
79+