`border-inline-width` CSS property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It's been available across browsers since September 2021.

The border-inline-width CSS property defines the width of the logical inline borders of an element, which maps to a physical border width depending on the element's writing mode, directionality, and text orientation. It corresponds to the border-top-width and border-bottom-width, or border-left-width, and border-right-width property depending on the values defined for writing-mode, direction, and text-orientation.

The border width in the other dimension can be set with border-block-width, which sets border-block-start-width, and border-block-end-width.

Try it

border-inline-width: thick;
writing-mode: horizontal-tb;

border-inline-width: thick;
writing-mode: vertical-rl;

border-inline-width: 4px;
writing-mode: horizontal-tb;
direction: rtl;

<section class="default-example" id="default-example">
  <div class="transition-all" id="example-element">
    This is a box with a border around it.
  </div>
</section>

#example-element {
  background-color: palegreen;
  color: black;
  border: 0 solid crimson;
  padding: 0.75em;
  width: 80%;
  height: 100px;
  unicode-bidi: bidi-override;
}

Syntax

/* <'line-width'> values */
border-inline-width: 5px 10px;
border-inline-width: 5px;
border-inline-width: thick;

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

Values

<line-width>: Defines the width of the border, either as an explicit non-negative <length> or the keywords: thin, medium, or thick. The default is medium.

Formal definition

Initial value	as each of the properties of the shorthand: `border-inline-start-width` `border-inline-end-width`
Applies to	all elements
Inherited	no
Computed value	as each of the properties of the shorthand: `border-inline-start-width` `border-inline-end-width`
Animation type	as each of the properties of the shorthand: `border-inline-start-width` `border-inline-end-width`

Formal syntax

border-inline-width = 
  <'border-top-width'>{1,2}

Examples

HTML

<div>
  <p class="exampleText">Example text</p>
</div>

CSS

div {
  background-color: yellow;
  width: 120px;
  height: 120px;
}

.exampleText {
  writing-mode: vertical-lr;
  border: 1px solid blue;
  border-inline-width: 5px 10px;
}

Specifications

Specification
CSS Logical Properties and Values Module Level 1 # propdef-border-inline-width

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`border-inline-width`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5
`medium`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5
`thick`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5
`thin`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5