offset-block-start

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

It relates to offset-block-end, offset-inline-start, and offset-inline-end, which define the other offsets of the element.

Initial value	auto
Applies to	positioned elements
Inherited	no
Percentages	logical-height of containing block
Media	visual
Computed value	same as box offsets: top, right, bottom, left properties except that directions are logical
Animation type	discrete
Canonical order	the unique non-ambiguous order defined by the formal grammar

Syntax

/* <length> values */
offset-block-start: 3px;
offset-block-start: 2.4em;

/* <percentage>s of the width or height of the containing block */
offset-block-start: 10%;

/* Keyword value */
offset-block-start: auto;

/* Global values */
offset-block-start: inherit;
offset-block-start: initial;
offset-block-start: unset;

Values

The offset-block-start property takes the same values as the left property.

Formal syntax

<'left'>

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;
  position: relative;
  offset-block-start: 20px;
  background-color: #c8c800;
}

Specification

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

Browser compatibility

[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

• The mapped physical properties: top, right, bottom, and left
• writing-mode, direction, text-orientation