HTMLImageElement: sizes property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2017.

The HTMLImageElement property sizes allows you to specify the layout width of the image for each of a list of media conditions. This provides the ability to automatically select among different images—even images of different orientations or aspect ratios—as the document state changes to match different media conditions.

Each condition is specified using the same conditional format used by media queries.

Value

A string containing a comma-separated list of source size descriptors followed by an optional fallback size. Each source size descriptor is comprised of a media condition, then at least one whitespace character, then the source size value to use for the image when the media condition evaluates to true. For more information about the syntax of the sizes attribute, see <img>.

Examples

Selecting an image to fit window width

In this example, a blog-like layout is created, displaying some text and an image for which three size points are specified, depending on the width of the window. Three versions of the image are also available, with their widths specified. The browser takes all of this information and selects an image and width that best meets the specified values.

How exactly the images are used may depend upon the browser and the pixel density of the user's display.

Buttons at the bottom of the example let you actually modify the sizes property slightly, switching the largest of the three widths for the image between 40em and 50em.

HTML

html
<article>
  <h1>An amazing headline</h1>
  <div class="test"></div>
  <p>
    This is even more amazing content text. It's really spectacular. And
    fascinating. Oh, it's also clever and witty. Award-winning stuff, I'm sure.
  </p>
  <img
    src="new-york-skyline-wide.jpg"
    srcset="
      new-york-skyline-wide.jpg 3724w,
      new-york-skyline-4by3.jpg 1961w,
      new-york-skyline-tall.jpg 1060w
    "
    sizes="((min-width: 50em) and (max-width: 60em)) 50em,
              ((min-width: 30em) and (max-width: 50em)) 30em,
              (max-width: 30em) 20em"
    alt="The New York City skyline on a beautiful day, with the One World Trade Center building in the middle." />
  <p>
    Then there's even more amazing stuff to say down here. Can you believe it? I
    sure can't.
  </p>

  <button id="break40">Last Width: 40em</button>
  <button id="break50">Last Width: 50em</button>
</article>

CSS

css
article {
  margin: 1em;
  max-width: 60em;
  min-width: 20em;
  border: 4em solid #880e4f;
  border-radius: 7em;
  padding: 1.5em;
  font:
    16px "Open Sans",
    Verdana,
    Arial,
    Helvetica,
    sans-serif;
}

article img {
  display: block;
  max-width: 100%;
  border: 1px solid #888;
  box-shadow: 0 0.5em 0.3em #888;
  margin-bottom: 1.25em;
}

JavaScript

The JavaScript code handles the two buttons that let you toggle the third width option between 40em and 50em; this is done by handling the click event, using the JavaScript string replace() method to replace the relevant portion of the sizes string.

js
const image = document.querySelector("article img");
const break40 = document.getElementById("break40");
const break50 = document.getElementById("break50");

break40.addEventListener(
  "click",
  () => (image.sizes = image.sizes.replace(/50em,/, "40em,")),
);

break50.addEventListener(
  "click",
  () => (image.sizes = image.sizes.replace(/40em,/, "50em,")),
);

Result

The page is best viewed in its own window, so you can adjust the sizes fully.

Specifications

Specification
HTML
# dom-img-sizes

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
sizes
auto value

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
See implementation notes.

See also