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 AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 29Edge ? Firefox No support NoIE Full support 10
Full support 10
Prefixed Requires 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

Contributors to this page: fscholz, mfluehr, Alhadis, johnsonjo4531, Sebastianz, mrenty, tuttza
Last updated by: fscholz,