border-block-width

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-block-width CSS property defines the width of the logical block 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.

Try it

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

Syntax

/* <'border-width'> values */
border-block-width: 5px;
border-block-width: thick;

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

Values

<'border-width'>: The width of the border. See border-width.

Formal definition

Initial value	`medium`
Applies to	all elements
Inherited	no
Percentages	logical-width of containing block
Computed value	absolute length; `0` if the border style is `none` or `hidden`
Animation type	by computed value type

Formal syntax

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

<border-top-width> = 
  <line-width>  

<line-width> = 
  <length [0,∞]>  |
  thin            |
  medium          |
  thick

Examples

Border width with vertical text

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-block-width: 5px;
}

Results

Specifications

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

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android
`border-block-width`	87	87	66	73	14.1	87	66	62	14.5	14.0	87