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block-size

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

The block-size CSS property defines the horizontal or vertical size of an element's block, depending on its writing mode. It corresponds to either the width or the height property, depending on the value of writing-mode.

Syntax

/* <length> values */
block-size: 300px;
block-size: 25em;

/* <percentage> values */
block-size: 75%;

/* Keyword values */
block-size: 25em border-box;
block-size: 75% content-box;
block-size: max-content;
block-size: min-content;
block-size: available;
block-size: fit-content;
block-size: auto;

/* Global values */
block-size: inherit;
block-size: initial;
block-size: unset;

If the writing mode is vertically oriented, the value of block-size relates to the width of the element; otherwise, it relates to the height of the element. A related property is inline-size, which defines the other dimension of the element.

Initial value auto
Applies to same as width and height
Inherited no
Percentages block-size of containing block
Media visual
Computed value same as width and height
Animation type discrete
Canonical order the unique non-ambiguous order defined by the formal grammar

Syntax

Values

The block-size property takes the same values as the width and height properties.

Formal syntax

<'width'>

Example

HTML

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

CSS

.exampleText {
  writing-mode: vertical-rl;
  background-color: yellow;
  block-size: 200px;
}

Specification

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

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 57 No 41
41
38 — 51
Disabled
Disabled 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.
No 44 No
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support 57 57 No 41
41
38 — 51
Disabled
Disabled 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.
44 No No

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/block-size