max-width

Summary

The max-width property is used to set the maximum width of a given element. It prevents the used value of the width property from becoming larger than the value specified for max-width.

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`
Animatable	yes, as a length, percentage or calc(); when both values are lengths, they are interpolated as lengths; when both values are percentages, they are interpolated as percentages; otherwise, both values are converted into a `calc()` function that is the sum of a length and a percentage (each possibly zero), and these `calc()` functions have each half interpolated as real numbers.
Canonical order	the unique non-ambiguous order defined by the formal grammar

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;
max-width: fill-available;

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

Values

none: The width has no maximum value.
<length>: See <length> for possible units.
<percentage>: Specified as a <percentage> of containing block's width.
max-content: The intrinsic preferred width.
min-content: The intrinsic minimum width.
fill-available: The containing block 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" <div> has its width property set so that it will use the full width of the parent <div> but the max-width property constrains its width to 150px.

<div id="parent">
    <div id="child">
        The Mozilla community produces a lot of great software.
    </div>
</div>

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

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

[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.