max-width - CSS: Cascading Style Sheets 编辑

The max-width CSS property sets the maximum width of an element. It prevents the used value of the width property from becoming larger than the value specified by max-width.

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The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

max-width overrides width, but min-width overrides max-width.

Syntax

/* <length> value */
max-width: 3.5em;

/* <percentage> value */
max-width: 75%;

/* Keyword values */
max-width: none;
max-width: max-content;
max-width: min-content;
max-width: fit-content(20em);

/* Global values */
max-width: inherit;
max-width: initial;
max-width: unset;

Values

<length>

Defines the max-width as an absolute value.

<percentage>

Defines the max-width as a percentage of the containing block's width.

none

No limit on the size of the box.

max-content

The intrinsic preferred max-width.

min-content

The intrinsic minimum max-width.

fit-content(<length-percentage>)

Uses the fit-content formula with the available space replaced by the specified argument, i.e. min(max-content, max(min-content, argument)).

Accessibility concerns

Ensure that elements set with a max-width are not truncated and/or do not obscure other content when the page is zoomed to increase text size.

• MDN Understanding WCAG, Guideline 1.4 explanations
• Understanding Success Criterion 1.4.4 | W3C Understanding WCAG 2.0

Formal definition

Initial value	none
Applies to	all elements but non-replaced inline elements, table rows, and row groups
Inherited	no
Percentages	refer to the width of the containing block
Computed value	the percentage as specified or the absolute length or none
Animation type	a length, percentage or calc();

Formal syntax

none | <length-percentage> | min-content | max-content | fit-content(<length-percentage>)
where 
<length-percentage> = <length> | <percentage>

Examples

Setting max width in pixels

In this example, the "child" will be either 150 pixels wide or the width of the "parent," whichever is smaller.

HTML

<div id="parent">
  <div id="child">
    Fusce pulvinar vestibulum eros, sed luctus ex lobortis quis.
  </div>
</div>

CSS

#parent {
  background: lightblue;
  width: 300px;
}

#child {
  background: gold;
  width: 100%;
  max-width: 150px;
}

Result

Specifications

Specification	Status	Comment
CSS Box Sizing Module Level 4 The definition of 'max-width' in that specification.	Editor's Draft
CSS Box Sizing Module Level 3 The definition of 'max-width' in that specification.	Working Draft	Adds the max-content, min-content, fit-content keywords.
CSS Level 2 (Revision 1) The definition of 'max-width' in that specification.	Recommendation	Initial definition.

Browser compatibility

BCD tables only load in the browser

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

• The box model, box-sizing
• width, min-width
• The mapped logical properties: max-inline-size, max-block-size