inset-block-start
Baseline Widely available *
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.
* Some parts of this feature may have varying levels of support.
Theinset-block-startCSS 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 thetop,right,bottom, orleft property depending on the values defined forwriting-mode,direction, andtext-orientation.
Thisinset property has no effect on non-positioned elements.
Try it
writing-mode: horizontal-tb;writing-mode: vertical-rl;writing-mode: horizontal-tb;direction: rtl;writing-mode: vertical-lr;<section> <div> <div> I am absolutely positioned with inset-block-start: 50px </div> <p> As much mud in the streets as if the waters had but newly retired from the face of the earth, and it would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling like an elephantine lizard up Holborn Hill. </p> </div></section>#example-element { border: 0.75em solid; padding: 0.75em; position: relative; width: 100%; min-height: 200px; unicode-bidi: bidi-override;}#abspos { background-color: yellow; color: black; border: 3px solid red; position: absolute; inset-block-start: 50px; inline-size: 140px;}Syntax
css
/* <length> values */inset-block-start: 3px;inset-block-start: 2.4em;inset-block-start: anchor(end);inset-block-start: calc(anchor-size(--my-anchor height, 70px) * 2);/* <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
Theinset-block-start property takes the same values as thetop 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 | alength,percentage or calc(); |
Formal syntax
inset-block-start =
auto|
<length-percentage>
<length-percentage> =
<length>|
<percentage>
Examples
Setting block start offset
HTML
html
<div> <p>Example text</p></div>CSS
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 Module Level 1 # propdef-inset-block-start |
| CSS Positioned Layout Module Level 3 # propdef-inset-block-start |
Browser compatibility
See also
- The properties that define other insets:
inset-block-end,inset-inline-start, andinset-inline-end - The mapped physical properties:
top,right,bottom, andleft writing-mode,direction,text-orientation