CSS max-width

<!doctype html>
<title>Example</title>
<style>
div { 
  background: gold;
  max-height: 60vh;
  max-width: 60vw;
  padding: 5vw;
  font-size: 7vw;
  overflow: auto;
  }
</style>
<div>Floccinaucinihilipilification of antidisestablishmentarianism.</div>

The CSS max-width property is used to constrain the width of an element. The element can render at any size up to the max-width, depending on its contents.

Syntax

Possible Values

length: Specifies a maximum value for width as a length value (for example 300px). Negative values are illegal.
percentage: Specifies a maximum value for width as a percentage of the width of the containing block. Negative values are illegal. If the containing block's width is negative, the used value is zero.
available: Equal to the containing block width minus the current element's margin, border, and padding.
min-content: The min-content width.
max-content: The max-content width.
fit-content: Same as max-content.
none: Specifies that there's no limit on the width of the box.

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

initial: Represents the value specified as the property's initial value.
inherit: Represents the computed value of the property on the element's parent.
unset: This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

General Information

Initial Value: none
Applies To: All elements except non-replaced inline elements, table rows, and row groups
Inherited?: No
Media: Visual
Animatable: Yes (see example)

Example Code

Here are some examples of valid max-width values:

Official Specifications

CSS basic box model (W3C Editor's Draft)
CSS Level 2.1 (W3C Recommendation 07 June 2011)