border-block-start-color

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

The border-block-start-color CSS property defines the color of the logical block-start border 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, border-right-color, border-bottom-color, or border-left-color property depending on the values defined for writing-mode, direction, and text-orientation.

Try it

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

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

border-block-start-color: rgb(170 50 220 / 0.6);
writing-mode: horizontal-tb;

border-block-start-color: hsl(60 90% 50% / 0.8);
writing-mode: vertical-lr;

<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: #eee;
  color: #000;
  border: 0.75em solid;
  padding: 0.75em;
  width: 80%;
  height: 100px;
  unicode-bidi: bidi-override;
}

Syntax

css

border-block-start-color: blue;
border-block-start-color: #4c5d21;

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

Related properties are border-block-end-color, border-inline-start-color, and border-inline-end-color, which define the other border colors of the element.

Values

<color>: The color of the border.

Formal definition

Initial value	`currentcolor`
Applies to	all elements
Inherited	no
Computed value	computed color
Animation type	by computed value type

Formal syntax

border-block-start-color = 
  <color>     |
  <image-1D>  

<image-1D> = 
  <stripes()>  

<stripes()> = 
  stripes( <color-stripe># )  

<color-stripe> = 
  <color>                            &&
  [ <length-percentage> | <flex> ]?  

<length-percentage> = 
  <length>      |
  <percentage>

Examples

Border color with vertical text

HTML

html

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

CSS

css

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

.exampleText {
  writing-mode: vertical-lr;
  border: 10px solid blue;
  border-block-start-color: red;
}

Results

Specifications

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