prefers-reduced-data

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Draft
This page is not complete.

Note: This feature is not supported by any user agent and its specifics are subject to change.

The prefers-reduced-data CSS media feature is used to detect if the user has requested the web content that consumes less internet traffic.

Syntax

no-preference
Indicates that the user has made no preference known to the system. This keyword value evaluates as false in the boolean context.
reduce
Indicates that user has expressed the preference for lightweight alternate content.

User preferences

Currently no user agent implements this feature, although various operating systems do support such preferences and if this media query is ever implemented user agents will likely rely on the settings provided by the operating system.

Examples

Note: No browser currently implements this feature so the following example will not work.

In this example the montserrat-regular.woff2 font file will neither be preloaded nor downloaded if the user prefers reduced data, in this case the "system font stack" will serve as the fallback font:

HTML

<head>
  <link rel="preload" href="fonts/montserrat-regular.woff2" as="font" media="(prefers-reduced-data: no-preference)" crossorigin>
  <link rel="stylesheet" href="style.css">
</head>

CSS

@media (prefers-reduced-data: no-preference) {
    @font-face {
        font-family: Montserrat;
        font-style: normal;
        font-weight: 400;
        font-display: swap;
        /* latin */
        src: local('Montserrat Regular'), local('Montserrat-Regular'), url('fonts/montserrat-regular.woff2') format('woff2');
        unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
    }
}

body {
  font-family: Montserrat, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, "Microsoft YaHei", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
}

Result

Specifications

Specification Status Comment
Media Queries Level 5
The definition of 'reduced-data' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
prefers-reduced-data media feature
Experimental
Chrome Full support 85
Notes Disabled
Full support 85
Notes Disabled
Notes See bug 1051189.
Disabled From version 85: this feature is behind the #enable-experimental-web-platform-features preference (needs to be set to Enabled). To change preferences in Chrome, visit chrome://flags.
Edge Full support 85
Notes Disabled
Full support 85
Notes Disabled
Notes See bug 1051189.
Disabled From version 85: this feature is behind the #enable-experimental-web-platform-features preference (needs to be set to Enabled).
Firefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android No support No
Notes
No support No
Notes
Notes See bug 1051189.
Chrome Android Full support 85
Notes Disabled
Full support 85
Notes Disabled
Notes See bug 1051189.
Disabled From version 85: this feature is behind the #enable-experimental-web-platform-features preference (needs to be set to Enabled). To change preferences in Chrome, visit chrome://flags.
Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also