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-widthborder-right-widthborder-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-widthborder-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
Mediavisual
Computed valueabsolute length; 0 if the border style is none or hidden
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar

Values

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

Formal syntax

<'border-top-width'>

Example

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;
}

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 compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
border-block-start-widthChrome Full support 69Edge No support NoFirefox 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 ?

Legend

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

See also