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LayoutShift

The LayoutShift interface of the Layout Instability API provides insights into the stability of web pages based on movements of the elements on the page.

PerformanceEntry LayoutShift

Properties

LayoutShift.value

Returns the impact fraction (fraction of the viewport that was shifted) times the distance fraction (distance moved as a fraction of viewport).

LayoutShift.hadRecentInput

Returns true if there was a user input in the past 500 milliseconds.

LayoutShift.lastInputTime

Returns the time of the most recent user input.

LayoutShift.sources

Returns an array of LayoutShiftAttribution objects with information on the elements that were shifted.

Methods

LayoutShift.toJSON()

Converts the properties to JSON.

Examples

The following example shows how to capture layout shifts and log them to the console.

Note that in this example data is only sent to the server when the user leaves the tab.

// Catch errors since some browsers throw when using the new `type` option.
// https://bugs.webkit.org/show_bug.cgi?id=209216
try {
  let cumulativeLayoutShiftScore = 0;

  const observer = new PerformanceObserver((list) => {
  for (const entry of list.getEntries()) {
    // Only count layout shifts without recent user input.
    if (!entry.hadRecentInput) {
      cumulativeLayoutShiftScore += entry.value;
    }
  }
  });

  observer.observe({type: 'layout-shift', buffered: true});

  document.addEventListener('visibilitychange', () => {
  if (document.visibilityState === 'hidden') {
    // Force any pending records to be dispatched.
    observer.takeRecords();
    observer.disconnect();

    console.log('CLS:', cumulativeLayoutShiftScore);
  }
  });
} catch (e) {
  // Do nothing if the browser doesn't support this API.
}

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
LayoutShift
77
79
No
No
64
No
77
77
No
55
No
12.0
hadRecentInput
77
79
No
No
64
No
77
77
No
55
No
12.0
lastInputTime
77
79
No
No
64
No
77
77
No
55
No
12.0
sources
84
84
No
No
70
No
84
84
No
60
No
14.0
toJSON
77
79
No
No
64
No
77
77
No
55
No
12.0
value
77
79
No
No
64
No
77
77
No
55
No
12.0

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/LayoutShift