This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.


The border-block-start-style CSS property defines the style of the logical block start border of an element, which maps to a physical border style depending on the element's writing mode, directionality, and text orientation. It corresponds to the border-top-styleborder-right-styleborder-bottom-style, or border-left-style property depending on the values defined for writing-mode, direction, and text-orientation.

It relates to border-block-end-styleborder-inline-start-style, and border-inline-end-style, which define the other border styles of the element.

Initial valuenone
Applies toall elements
Computed valueas specified
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar


border-block-start-style: dashed;
border-block-start-style: dotted;
border-block-start-style: groove;


See border-style

Formal syntax



HTML Content

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

CSS Content

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

.exampleText {
  writing-mode: vertical-lr;
  border: 5px solid blue;
  border-block-start-style: dashed;


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support No support 41.0 (41.0)[1] No support No support No support
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support No support 41.0 (41.0)[1] No support No support No support

[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

Document Tags and Contributors

 Contributors to this page: teoli, Sebastianz, fscholz, jsx, kscarfone
 Last updated by: teoli,