inset-block CSS property

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.

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

This inset property has no effect on non-positioned elements.

Try it

inset-block: 10px 20px;
writing-mode: horizontal-tb;
inset-block: 20px 40px;
writing-mode: vertical-rl;
inset-block: 5% 20%;
writing-mode: horizontal-tb;
inset-block: 1rem auto;
writing-mode: vertical-lr;
<section id="default-example">
  <div class="example-container">
    <div id="example-element">I am absolutely positioned.</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-container {
  border: 0.75em solid #ad1457;
  padding: 0.75em;
  text-align: left;
  position: relative;
  width: 100%;
  min-height: 200px;
}

#example-element {
  background-color: #07136c;
  border: 6px solid #ffa000;
  color: white;
  position: absolute;
  inset: 0;
}

Constituent properties

This property is a shorthand for the following CSS properties:

Syntax

css
/* <length> values */
inset-block: 3px 10px;
inset-block: 2.4em 3em;
inset-block: 10px; /* value applied to start and end */
inset-block: auto anchor(start);
inset-block: 10em anchor-size(--my-anchor height, 10%);

/* <percentage>s of the width or height of the containing block */
inset-block: 10% 5%;

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

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

Values

The inset-block property takes the same values as the top property.

Formal definition

Initial valueas each of the properties of the shorthand:
Applies topositioned elements
Inheritedno
Percentageslogical-height of containing block
Computed valueas each of the properties of the shorthand:
Animation typea length, percentage or calc();

Formal syntax

inset-block = 
<'top'>{1,2}

<top> =
auto |
<length-percentage> |
<anchor()> |
<anchor-size()>

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

<anchor()> =
anchor( <anchor-name>? &&
<anchor-side> , <length-percentage>? )

<anchor-size()> =
anchor-size( [ <anchor-name> || <anchor-size> ]? , <length-percentage>? )

<anchor-name> =
<dashed-ident>

<anchor-side> =
inside |
outside |
top |
left |
right |
bottom |
start |
end |
self-start |
self-end |
<percentage> |
center

<anchor-size> =
width |
height |
block |
inline |
self-block |
self-inline

Examples

Setting block start and end offsets

HTML

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

CSS

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

.exampleText {
  writing-mode: vertical-lr;
  position: relative;
  inset-block: 20px 50px;
  background-color: #c8c800;
}

Result

Specifications

Specification
CSS Logical Properties and Values Module Level 1
# propdef-inset-block
CSS Positioned Layout Module Level 3
# propdef-inset-block

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
inset-block
Chrome – Full support
Chrome 87 (Release date: 2020-11-17)
footnote Full support
Edge – Full support
Edge 87 (Release date: 2020-11-19)
footnote Full support
Firefox – No support
Firefox 41 – 62 (Release date: 2015-09-22)
altname
altname Alternate name: offset-block
Firefox – Full support
Firefox 63 (Release date: 2018-10-23)
footnote Full support
Opera – Full support
Opera 73 (Release date: 2020-12-09)
footnote Full support
Safari – Full support
Safari 14.1 (Release date: 2021-04-26)
footnote Full support
Chrome Android – Full support
Chrome Android 87 (Release date: 2020-11-17)
footnote Full support
Firefox for Android – No support
Firefox for Android 41 – 62 (Release date: 2015-09-22)
altname
altname Alternate name: offset-block
Firefox for Android – Full support
Firefox for Android 63 (Release date: 2018-10-23)
footnote Full support
Opera Android – Full support
Opera Android 62 (Release date: 2021-02-16)
footnote Full support
Safari on iOS – Full support
Safari on iOS 14.5 (Release date: 2021-04-26)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 87 (Release date: 2020-11-17)
footnote Full support
WebView on iOS – Full support
WebView on iOS 14.5 (Release date: 2021-04-26)
footnote Full support
anchor()
Chrome – Full support
Chrome 125 (Release date: 2024-05-14)
footnote Full support
Edge – Full support
Edge 125 (Release date: 2024-05-17)
footnote Full support
Firefox – Full support
Firefox 147 (Release date: 2026-01-13)
footnote Full support
Opera – Full support
Opera 111 (Release date: 2024-06-12)
footnote Full support
Safari – Full support
Safari 26 (Release date: 2025-09-15)
footnote Full support
Chrome Android – Full support
Chrome Android 125 (Release date: 2024-05-14)
footnote Full support
Firefox for Android – Full support
Firefox for Android 147 (Release date: 2026-01-13)
footnote Full support
Opera Android – Full support
Opera Android 83 (Release date: 2024-06-25)
footnote Full support
Safari on iOS – Full support
Safari on iOS 26 (Release date: 2025-09-15)
footnote Full support
Samsung Internet – Full support
Samsung Internet 27 (Release date: 2024-11-06)
footnote Full support
WebView Android – Full support
WebView Android 125 (Release date: 2024-05-14)
footnote Full support
WebView on iOS – Full support
WebView on iOS 26 (Release date: 2025-09-15)
footnote Full support
anchor-size()
Chrome – Full support
Chrome 132 (Release date: 2025-01-14)
footnote Full support
Edge – Full support
Edge 132 (Release date: 2025-01-17)
footnote Full support
Firefox – Full support
Firefox 147 (Release date: 2026-01-13)
footnote Full support
Opera – Full support
Opera 117 (Release date: 2025-02-13)
footnote Full support
Safari – Full support
Safari 26 (Release date: 2025-09-15)
footnote Full support
Chrome Android – Full support
Chrome Android 132 (Release date: 2025-01-14)
footnote Full support
Firefox for Android – Full support
Firefox for Android 147 (Release date: 2026-01-13)
footnote Full support
Opera Android – Full support
Opera Android 87 (Release date: 2025-01-22)
footnote Full support
Safari on iOS – Full support
Safari on iOS 26 (Release date: 2025-09-15)
footnote Full support
Samsung Internet – Full support
Samsung Internet 29 (Release date: 2025-10-25)
footnote Full support
WebView Android – Full support
WebView Android 132 (Release date: 2025-01-14)
footnote Full support
WebView on iOS – Full support
WebView on iOS 26 (Release date: 2025-09-15)
footnote Full support
auto
Chrome – Full support
Chrome 87 (Release date: 2020-11-17)
footnote Full support
Edge – Full support
Edge 87 (Release date: 2020-11-19)
footnote Full support
Firefox – Full support
Firefox 41 (Release date: 2015-09-22)
footnote Full support
Opera – Full support
Opera 73 (Release date: 2020-12-09)
footnote Full support
Safari – Full support
Safari 14.1 (Release date: 2021-04-26)
footnote Full support
Chrome Android – Full support
Chrome Android 87 (Release date: 2020-11-17)
footnote Full support
Firefox for Android – Full support
Firefox for Android 41 (Release date: 2015-09-22)
footnote Full support
Opera Android – Full support
Opera Android 62 (Release date: 2021-02-16)
footnote Full support
Safari on iOS – Full support
Safari on iOS 14.5 (Release date: 2021-04-26)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 87 (Release date: 2020-11-17)
footnote Full support
WebView on iOS – Full support
WebView on iOS 14.5 (Release date: 2021-04-26)
footnote Full support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
Uses a non-standard name
Has more compatibility info.

See also