ResizeObserverEntry: contentRect property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2020.

The contentRect read-only property of the ResizeObserverEntry interface returns a DOMRectReadOnly object containing the new size of the observed element when the callback is run. Note that this is better supported than ResizeObserverEntry.borderBoxSize or ResizeObserverEntry.contentBoxSize, but it is left over from an earlier implementation of the Resize Observer API, is still included in the spec for web compat reasons, and may be deprecated in future versions.

Value

A DOMRectReadOnly object containing the new size of the element indicated by the target property.

If the target is an HTML Element, the returned contentRect is the element's content box. If the target is an SVGElement, the returned contentRect is the SVG's bounding box.

Examples

The following snippet is taken from the resize-observer-text.html (see source) example. This uses a simple feature detection test to see if the browser supports the newer ResizeObserverEntry.contentBoxSize property — if so, it uses that to get the sizing data it needs. If not, it uses contentRect.

js
const resizeObserver = new ResizeObserver((entries) => {
  for (const entry of entries) {
    if (entry.contentBoxSize) {
      h1Elem.style.fontSize = `${Math.max(
        1.5,
        entry.contentBoxSize.inlineSize / 200,
      )}rem`;
      pElem.style.fontSize = `${Math.max(
        1,
        entry.contentBoxSize.inlineSize / 600,
      )}rem`;
    } else {
      h1Elem.style.fontSize = `${Math.max(
        1.5,
        entry.contentRect.width / 200,
      )}rem`;
      pElem.style.fontSize = `${Math.max(1, entry.contentRect.width / 600)}rem`;
    }
  }
});

resizeObserver.observe(divElem);

Specifications

Specification
Resize Observer
# dom-resizeobserverentry-contentrect

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
contentRect

Legend

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Full support
Full support