LayoutShiftAttribution

LayoutShiftAttribution.Node Read only

Returns the element that has shifted (null if it has been removed).

LayoutShiftAttribution.previousRect Read only Experimental

Returns a DOMRectReadOnly object representing the position of the element before the shift.

LayoutShiftAttribution.currentRect Read only Experimental

Returns a DOMRectReadOnly object representing the position of the element after the shift.

LayoutShiftAttribution.toJSON() Experimental

Returns a JSON representation of the LayoutShiftAttribution object.

The following example finds the element that is causing the largest layout shift, and prints that node to the console. For more detail on this see Debug Web Vitals in the field.

function getCLSDebugTarget(entries) {
  const largestEntry = entries.reduce((a, b) => a && a.value > b.value ? a : b);
  if (largestEntry?.sources?.length) {
    const largestSource = largestEntry.sources.reduce((a, b) => {
      const area = (el) => el.previousRect.width * el.previousRect.height;
      return a.node && area(a) > area(b) ? a : b;
    });
    if (largestSource) {
      return largestSource.node;
    }
  }
}

• Debug layout shifts
• Debug Web Vitals in the field