LayoutShiftAttribution

The LayoutShiftAttribution interface of the Layout Instability API provides debugging information about elements which have shifted.

Instances of LayoutShiftAttribution are returned in an array by calling LayoutShift.sources.

LayoutShiftAttribution.NodeRead only

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

LayoutShiftAttribution.previousRectRead only

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

LayoutShiftAttribution.currentRectRead only

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

LayoutShiftAttribution.toJSON()

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

• Debug layout shifts
• Debug Web Vitals in the field