border-inline-start-width

Defines the thickness of the logical 'start' border. It's the modern way to set a left border that flips to the right in RTL languages.

It is documented as part of the CSS Logical Properties and Values specification.

/* Usage Example */
.side-accent {
  /* Logical left border thickness */
  border-inline-start-width: 8px;
  border-inline-start-style: solid;
  border-inline-start-color: #ec4899;
}

/* Syntax */
border-inline-start-width: border-top-width;

/* Global values */
border-inline-start-width: inherit;
border-inline-start-width: initial;
border-inline-start-width: revert;
border-inline-start-width: revert-layer;
border-inline-start-width: unset;
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.

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