`min-block-size` 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 September 2021.

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

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

Try it

min-block-size: 150px;
writing-mode: horizontal-tb;

min-block-size: 150px;
writing-mode: vertical-rl;

min-block-size: 20px;
writing-mode: horizontal-tb;

min-block-size: 15em;
writing-mode: vertical-lr;

<section class="default-example" id="default-example">
  <div class="transition-all" id="example-element">
    This is a box where you can change the minimum block size. <br />If there is
    more content than the minimum the box will grow in the block dimension as
    needed by the content.
  </div>
</section>

#example-element {
  display: flex;
  flex-direction: column;
  background-color: #5b6dcd;
  justify-content: center;
  color: white;
}

Syntax

/* <length> values */
min-block-size: 100px;
min-block-size: 5em;
min-block-size: anchor-size(self-inline);

/* <percentage> values */
min-block-size: 10%;

/* Keyword values */
min-block-size: max-content;
min-block-size: min-content;
min-block-size: fit-content;
min-block-size: fit-content(20em);

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

Values

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

Formal definition

Initial value	0
Applies to	same as `width` and `height`
Inherited	no
Percentages	block-size of containing block
Computed value	same as `min-width` and `min-height`
Animation type	$1$, <a href="/en-US/docs/Web/CSS/Reference/Values/percentage#interpolation" title="Values of the <percentage> CSS data type are interpolated as real, floating-point numbers.">percentage</a> or calc();

Formal syntax

min-block-size = 
  <'min-width'>

Examples

Setting minimum block size for vertical text

HTML

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

CSS

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

Result

Specifications

Specification
CSS Logical Properties and Values Module Level 1 # propdef-min-block-size
CSS Box Sizing Module Level 3 # sizing-values

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
`min-block-size`	57	79	41	44	12.1	57	41	43	12.2	7.0	57	12.2
`anchor-size`	125	125	147	111	26	125	147	83	26	27.0	125	26
`auto`	57	79	41	44	12.1	57	41	43	12.2	7.0	57	12.2
`fit-content`	57	79	94	44	12.1	57	94	43	12.2	7.0	57	12.2
`fit-content_function`	No	No	91	No	No	No	No	No	No	No	No	No
`max-content`	57	79	66 41	44	12.1	57	66 41	43	12.2	7.0	57	12.2
`min-content`	57	79	66 41	44	12.1	57	66 41	43	12.2	7.0	57	12.2
`stretch`	138	138	No	122	27	138	No	91	27	30.0	138	27