The zoom CSS descriptor sets the initial zoom factor of a document defined by the @viewport at-rule.

A zoom factor of 1.0 or 100% corresponds to no zooming. Larger values are zoomed in. Smaller values are zoomed out.


/* Keyword value */
zoom: auto;

/* <number> values */
zoom: 0.8;
zoom: 2.0;

/* <percentage> values */
zoom: 150%;


The user agent will set the document's initial zoom factor. The user agent may use the size of canvas area on which the document is rendered to determine that factor.
A non-negative number used as the zoom factor.
A non-negative percentage value used as the zoom factor.

Formal definition

Related at-rule@viewport
Initial valueauto
Percentagesthe zoom factor itself
Computed valueauto, or a non-negative number or percentage as specified

Formal syntax

auto | <number> | <percentage>


Setting viewport zoom factor

@viewport {
  zoom: 2.0;


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
zoom descriptorChrome No support 29 — 84Edge Full support 12
Full support 12
Prefixed Implemented with the vendor prefix: -ms-
Firefox No support NoIE Full support 10
Full support 10
Prefixed Implemented with the vendor prefix: -ms-
Opera Full support 16Safari No support NoWebView Android No support 4.4 — 37Chrome Android No support 61 — 84Firefox Android No support NoOpera Android Full support 16Safari iOS No support NoSamsung Internet Android Full support 8.0


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

See also