The max-width CSS descriptor specifies the maximum width of the viewport of a document defined via the @viewport at-rule.

By default, the width is set as close as possible to the initial viewport considering the maximum width constraint.

Related at-rule@viewport
Initial valueauto
Percentagesrefer to the width of the initial viewport
Mediaas each of the properties of the shorthand:
Computed valueif specified as a length, the corresponding absolute length; if specified as a percentage, the specified value; otherwise, auto
Canonical orderthe unique non-ambiguous order defined by the formal grammar


/* Keyword value */
max-width: auto;

/* <length> values */
max-width: 600px;
max-width: 80em;
max-width: 15cm;

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


The used value is calculated from the other CSS descriptors' values.
A non-negative absolute or relative length.
A percentage value relative to the width of the initial viewport at zoom factor 1.0 for horizontal lengths. Must be non-negative.

Formal syntax


<viewport-length> = auto | <length-percentage>

<length-percentage> = <length> | <percentage>


Specification Status Comment
CSS Device Adaptation
The definition of '"max-width" descriptor' in that specification.
Working Draft Initial definition

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 29Edge ? Firefox No support NoIE Full support 10
Full support 10
Prefixed Implemented with the vendor prefix: -ms-
Opera Full support 16
Full support 16
No support 11.1 — 15
Safari No support NoWebView Android Full support 4.4Chrome Android Full support 29Edge Mobile ? Firefox Android No support NoOpera Android Full support 16
Full support 16
No support 11.1 — 14
Safari iOS No support NoSamsung Internet Android Full support Yes


Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Requires a vendor prefix or different name for use.
Requires a vendor prefix or different name for use.

Document Tags and Contributors

Last updated by: mdnwebdocs-bot,