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border-block-start-width

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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.

Syntax

/* <'border-width'> values */
border-block-start-width: 5px;
border-block-start-width: thick;

Related properties are 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

Values

<'border-width'>: The width of the border. 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 and Values Level 1 The definition of 'border-block-start-width' in that specification.	Editor's Draft	Initial definition

Browser compatibilityUpdate compatibility data on GitHub

	Desktop
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	69	No	41 41 38 — 51 Disabled Disabled From version 38 until version 51 (exclusive): this feature is behind the `layout.css.vertical-text.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	No	56	No

	Mobile
	Android webview	Chrome for Android	Edge Mobile	Firefox for Android	Opera for Android	iOS Safari	Samsung Internet
Basic support	69	?	No	41 41 38 — 51 Disabled Disabled From version 38 until version 51 (exclusive): this feature is behind the `layout.css.vertical-text.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	56	No	?