The width CSS descriptor is shorthand for setting both the min-width and the max-width descriptors of the viewport. By providing one viewport length value, that value will determine both the min-width and the max-width to the value provided.

If two viewport values are provided the first value will be set to the min-width and the second value will be set max-width.


/* An example with one viewport value: */
@viewport {
    width: 320px;

/* An example with two viewport values: */
@viewport {
    width: 320px, 120px;


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 or height of the initial viewport at zoom factor 1.0, for horizontal and vertical lengths respectively. Must be non-negative.

Formal syntax


Specification Status Comment
CSS Device Adaptation
"min-width" descriptor
Working Draft Initial definition

Browser compatibility

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Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 29 (behind a flag) 未实现 10 -ms 11.10
Removed in 15
Reintroduced behind a flag in 16
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support
未实现 10-ms 11.10
Removed in 15
Reintroduced behind a flag in 16