border-block-start-width

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

It relates to border-block-end-width, border-inline-start-width, and border-inline-end-width, which define the other border widths of the element.

Initial value	medium
Applies to	all elements
Inherited	no
Percentages	logical-width of containing block
Media	visual
Computed value	absolute length; 0 if the border style is none or hidden
Animation type	discrete
Canonical order	the unique non-ambiguous order defined by the formal grammar

Syntax

/* border-block-start-width: width */
border-block-start-width: 5px;

border-block-start-width: inherit;

Values

<'border-width'>

See border-width

Formal syntax

<'border-width'>

Example

HTML Content

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

CSS Content

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

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

Specification

Specification	Status	Comment
CSS Logical Properties Level 1 The definition of 'border-block-start-width' in that specification.	Editor's Draft	Initial definition

Browser compatibility

[1] Available since Gecko 38, but behind the preference layout.css.vertical-text.enabled, then disabled by default. The preference has been removed in Gecko 51 and this property cannot be disabled since this version.

See also

• The mapped physical properties: border-top-width, border-right-width, border-bottom-width, and border-left-width
• writing-mode, direction, text-orientation