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 valuemedium
Applies toall elements
Inheritedno
Percentageslogical-width of containing block
Computed valueabsolute length; 0 if the border style is none or hidden
Animation typea length

Values

<'border-width'>
The width of the border. See border-width.

Formal definition

Initial valuemedium
Applies toall elements
Inheritedno
Percentageslogical-width of containing block
Computed valueabsolute length; 0 if the border style is none or hidden
Animation typea length

Formal syntax

<'border-top-width'>

Examples

Border width with vertical text

HTML

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

CSS

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

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

Results

Specifications

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 compatibility

DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
border-block-start-widthChrome Full support 69Edge Full support 79Firefox Full support 41
Full support 41
No support 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.
IE No support NoOpera Full support 56Safari Full support 12.1WebView Android Full support 69Chrome Android Full support 69Firefox Android Full support 41
Full support 41
No support 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.
Opera Android Full support 48Safari iOS Full support 12.2Samsung Internet Android Full support 10.0

Legend

Full support
Full support
No support
No support
User must explicitly enable this feature.
User must explicitly enable this feature.

See also