Web/CSS/image-set()

The image-set() CSS function notation is a method of letting the browser pick the most appropriate CSS image from a given set, primarily for high pixel density screens.

Resolution and bandwidth differ by device and network access. The image-set() function delivers the most appropriate image resolution for a user’s device, providing a set of image options — each with an associated resolution declaration — from which the browser picks the most appropriate for the device and settings. Resolution can be used as a proxy for filesize — a user agent on a slow mobile connection with a high-resolution screen may prefer to receive lower-resolution images rather than waiting for a higher resolution image to load.

image-set() allows the author to provide options rather than determining what each individual user needs.

Syntax

image-set() = image-set( <image-set-option># ) 
where <image-set-option> = [ <image> | <string> ] <resolution> and
      <string> is an <url>

Values

Most commonly you'll see an url() <string> value, but the <image> can be any image type except for an image set. The image-set() function can not be nested inside another image-set() function.

<resolution> units include x or dppx, for dots per pixel unit, dpi, for dots per inch, and dpcm for dots per centimeter. Every image within an image-set() must have a unique resolution.

Examples

Using image-set() to provide alternative background-image options

background-image: image-set( "cat.png" 1x,
                             "cat-2x.png" 2x,
                             "cat-print.png" 600dpi);

This example shows how to use image-set() to provide two alternative background-image options, chosen depending on the resolution needed: a normal version and a high-resolution version.

Accessibility concerns

Browsers do not provide any special information on background images to assistive technology. This is important primarily for screen readers, as a screen reader will not announce its presence and therefore convey nothing to its users. If the image contains information critical to understanding the page's overall purpose, it is better to describe it semantically in the document.

Specifications

Specification	Status	Comment
CSS Images Module Level 4The definition of 'The image-set() notation' in that specification.	Working Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`image-set()`	Chrome Full support 21 Prefixed' Full support 21 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Edge Full support 79 Prefixed' Full support 79 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Firefox No support No Notes' No support No Notes' Notes' See bug 1107646.	IE No support No	Opera Full support 15 Prefixed' Full support 15 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Safari Partial support 6 Prefixed' Notes' Partial support 6 Prefixed' Notes' Prefixed' Implemented with the vendor prefix: -webkit- Notes' Support for `url` images only and `x` is the only supported resolution unit. See bug 160934.	WebView Android Full support 4.4 Prefixed' Full support 4.4 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Chrome Android Full support 25 Prefixed' Full support 25 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Firefox Android No support No Notes' No support No Notes' Notes' See bug 1107646.	Opera Android Full support 14 Prefixed' Full support 14 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-	Safari iOS Partial support 6 Prefixed' Notes' Partial support 6 Prefixed' Notes' Prefixed' Implemented with the vendor prefix: -webkit- Notes' Support for `url` images only and `x` is the only supported resolution unit. See bug 160934.	Samsung Internet Android Full support 1.5 Prefixed' Full support 1.5 Prefixed' Prefixed' Implemented with the vendor prefix: -webkit-

Legend

Full support: Full support
Partial support: Partial support
No support: No support
See implementation notes.': See implementation notes.
Requires a vendor prefix or different name for use.': Requires a vendor prefix or different name for use.