max-width

The max-width CSS property is used to set 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.

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

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

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
Media	visual
Computed value	the percentage as specified or the absolute length or `none`
Animation type	a length, percentage or calc();
Canonical order	the unique non-ambiguous order defined by the formal grammar

Syntax

Values

<length>: The maximum width, expressed as a <length>.
<percentage>: The maximum width, expressed as a <percentage> of the containing block's width.
none: The width has no maximum value.
max-content: The intrinsic preferred width.
min-content: The intrinsic minimum width.
fill-available: The containing block's width minus horizontal margin, border, and padding. Some browsers implement an ancient name for this keyword, available.
fit-content: The same as max-content.

Formal syntax

<length> | <percentage> | none | max-content | min-content | fit-content | fill-available

Examples

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

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

#parent {
  background: lightblue;
  width: 300px;
}
#child {
  background: gold;
  width: 100%;
  max-width: 150px;
}

The fit-content value can be used to set the width of an element based on the intrinsic size required by its content:

<div id="parent">
    <div id="child">
        Child Text
    </div>
</div>

#parent {
  background: lightblue;
  width: 300px;
}
#child  {
  background: gold;
  width: 100%;
  max-width: -moz-fit-content;
  max-width: -webkit-fit-content;
}

Specifications

Specification	Status	Comment
CSS Intrinsic & Extrinsic Sizing Module Level 3 The definition of 'max-width' in that specification.	Working Draft	Adds the `max-content`, `min-content`, `fit-content`, and `fill-available` keywords. Both CSS3 Box and CSS3 Writing Modes drafts defined at some point these keywords. These drafts are superseded by this spec.
CSS Transitions The definition of 'max-width' in that specification.	Working Draft	Defines `max-width` as animatable.
CSS Level 2 (Revision 1) The definition of 'max-width' in that specification.	Recommendation	Initial definition

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	1.0	(Yes)	1.0 (1.7 or earlier)	7.0	4.0	2.0.2 (416), buggy before
applies to `<table>` [1]	No support	No support	(Yes)	No support	(Yes)	No support
`max-content`, `min-content`, `fit-content`, and `fill-available`	No support [3]	No support	3.0 (1.9)-moz [2]	No support	No support	No support [3]

Feature	Android	Edge	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile
Basic support	?	(Yes)	?	?	?	?

[1] CSS 2.1 explicitly leaves the behavior of max-width with <table> undefined. Therefore any behavior is CSS2.1-compliant; newer CSS specifications may define this behavior, so Web developers shouldn't rely on a specific one now.

[2] Gecko experimentally implements the definitions given in CSS3 Basic Box. This one defines available and not fill-available. Also the definition of fit-content is simpler than in CSS3 Sizing.

[3] WebKit implements an earlier proposal for setting the height to an intrinsic height: the keywords intrinsic, instead of max-content, and min-intrinsic, instead of min-content There is no equivalent for fill-available or fit-content.