inset-block-start

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The inset-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 toprightbottom, or left property depending on the values defined for writing-mode, direction, and text-orientation.

Note: Prior to Firefox 63 this property was implemented as offset-block-start. Firefox 63 updated the name of this property to match a change to the specification.

/* <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: unset;

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

Initial valueauto
Applies topositioned elements
Inheritedno
Percentageslogical-height of containing block
Mediavisual
Computed valuesame as box offsets: top, right, bottom, left properties except that directions are logical
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar

Syntax

Values

The inset-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;
  inset-block-start: 20px;
  background-color: #c8c800;
}

Specification

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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No ?

63

41 — 631

38 — 512

No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No ? ?

63

41 — 631

38 — 512

No No No

1. Supported as offset-block-start.

2. From version 38 until version 51 (exclusive): this feature is behind the layout.css.vertical-text.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

See also

Document Tags and Contributors

Last updated by: chrisdavidmills,