This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.


The inline-size CSS property defines the horizontal or vertical size of an element's block depending on it's writing mode. It corresponds to the width or the height property depending on the value defined for writing-mode.

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

Initial valueauto
Applies tosame as width and height
Percentagesinline-size of containing block
Computed valuesame as width and height
Canonical orderthe unique non-ambiguous order defined by the formal grammar


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

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

/* Keyword values */
inline-size: border-box;
inline-size: content-box;
inline-size: max-content;
inline-size: min-content;
inline-size: available;
inline-size: fit-content;
inline-size: auto;

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


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

Formal syntax



HTML Content

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

CSS Content

.exampleText {
  writing-mode: vertical-rl;
  background-color: yellow;
  inline-size: 110px;


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support Not supported 41.0 (41.0)[1] Not supported Not supported Not supported
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support Not supported 41.0 (41.0)[1] Not supported Not supported Not supported

[1] Available since Gecko 38, but behind the preference layout.css.vertical-text.enabled, then disabled by default.

See also

Document Tags and Contributors

 Contributors to this page: Sebastianz, fscholz, teoli, hbloomer
 Last updated by: Sebastianz,