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

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

Try it

border-block-color: red;
writing-mode: horizontal-tb;

border-block-color: #32a1ce;
writing-mode: vertical-rl;

border-block-color: rgb(170 50 220 / 0.6);
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: #eeeeee;
  color: black;
  border: 0.75em solid;
  padding: 0.75em;
  width: 80%;
  height: 100px;
  unicode-bidi: bidi-override;
}

Syntax

border-block-color: yellow;
border-block-color: #f5f6f7;

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

Values

This property is specified as one <color> value:

color: The color of the border.

Formal definition

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

Formal syntax

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

Examples

Border 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: 10px solid blue;
  border-block-color: red;
}

Results

Specifications

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

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-block-color`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5
`currentColor`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5
`transparent`	87	87	66	73	14.1	87	66	62	14.5	14.0	87	14.5