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inset-block-start

The inset-block-start CSS property defines the logical block start offset of an element, which maps to a physical inset 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.

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Syntax

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

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

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

/* Global values */
inset-block-start: inherit;
inset-block-start: initial;
inset-block-start: revert;
inset-block-start: revert-layer;
inset-block-start: unset;

Values

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

Formal definition

Initial value	`auto`
Applies to	positioned elements
Inherited	no
Percentages	logical-height of containing block
Computed value	same as box offsets: `top`, `right`, `bottom`, `left` properties except that directions are logical
Animation type	a length, percentage or calc();

Formal syntax

inset-block-start = 
  auto                 |
  <length-percentage>  

<length-percentage> = 
  <length>      |
  <percentage>

Examples

Setting block start offset

HTML

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

CSS

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

.exampleText {
  writing-mode: vertical-lr;
  position: relative;
  inset-block-start: 20px;
  background-color: #c8c800;
}

Result

Specifications

Specification
CSS Logical Properties and Values Level 1 # position-properties

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`inset-block-start`	87	87	6341–63	No	73	14.1	87	87	6341–63	62	14.5	14.0