border-block-start

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.

This property is a shorthand for the following CSS properties:

• border-block-start-color
• border-block-start-style
• border-block-start-width

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: 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:

<'border-width'>

The width of the border. See border-width.

<'border-style'>

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

<'color'>

The color of the border. See color.

<'border-top-width'> || <'border-top-style'> || <color>
where 
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hwb()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
where 
<rgb()> = rgb( <percentage>{3} [ / <alpha-value> ]? ) | rgb( <number>{3} [ / <alpha-value> ]? ) | rgb( <percentage>#{3} , <alpha-value>? ) | rgb( <number>#{3} , <alpha-value>? )
<rgba()> = rgba( <percentage>{3} [ / <alpha-value> ]? ) | rgba( <number>{3} [ / <alpha-value> ]? ) | rgba( <percentage>#{3} , <alpha-value>? ) | rgba( <number>#{3} , <alpha-value>? )
<hsl()> = hsl( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsl( <hue>, <percentage>, <percentage>, <alpha-value>? )
<hsla()> = hsla( <hue> <percentage> <percentage> [ / <alpha-value> ]? ) | hsla( <hue>, <percentage>, <percentage>, <alpha-value>? )
<hwb()> = hwb( [<hue> | none] [<percentage> | none] [<percentage> | none] [ / [<alpha-value> | none] ]? )
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>

HTML

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

CSS

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

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

• This property maps to one of the physical border properties: border-top, border-right, border-bottom, or border-left.
• writing-mode, direction, text-orientation