LayoutShiftAttribution

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The LayoutShiftAttribution interface provides debugging information about elements which have shifted.

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

Instance properties

LayoutShiftAttribution.node Read only Experimental

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.

Instance methods

LayoutShiftAttribution.toJSON() Experimental

Returns a JSON representation of the LayoutShiftAttribution object.

Examples

The following example finds the element with the highest layout shift score, and returns the element in that entry with the largest size prior to the shift (previousRect). For more detail on this see Debug Web Vitals in the field.

js
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;
    }
  }
}

Specifications

Specification
Layout Instability
# sec-layout-shift-attribution

Browser compatibility

BCD tables only load in the browser

See also