The border-block-start CSS property is a shorthand property for setting the individual logical block-start border property values in a single place in the style sheet.

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Constituent properties

This property is a shorthand for the following CSS properties:


border-block-start: 1px;
border-block-start: 2px dotted;
border-block-start: medium dashed blue;

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

border-block-start can be used to set the values for one or more of border-block-start-width, border-block-start-style, and border-block-start-color. The physical border to which it maps depends on the element's writing mode, directionality, and text orientation. It corresponds to the border-top, border-right, border-bottom, or border-left property depending on the values defined for writing-mode, direction, and text-orientation.

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


The border-block-start is specified with one or more of the following, in any order:


The width of the border. See border-width.


The line style of the border. See border-style.


The color of the border.

Formal definition

Initial value as each of the properties of the shorthand:
Applies to all elements
Inherited no
Computed value as each of the properties of the shorthand:
Animation type as each of the properties of the shorthand:

Formal syntax

border-block-start = 
<'border-top-width'> ||
<'border-top-style'> ||


Border with vertical text


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


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

.exampleText {
  writing-mode: vertical-rl;
  border-block-start: 5px dashed blue;


Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
border-block-start 69 79 41 No 56 12.1 69 69 41 48 12.2 10.0

See also

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