LargestContentfulPaint

The LargestContentfulPaint interface of the Largest Contentful Paint API provides details about the largest image or text paint before user input on a web page. The timing of this paint is a good heuristic for when the main page content is available during load.

Properties

This interface also inherits properties from PerformanceEntry.

LargestContentfulPaint.elementRead only: The element that is the current largest contentful paint.
LargestContentfulPaint.renderTimeRead only: The time the element was rendered to the screen. May not be available if the element is a cross-origin image loaded without the Timing-Allow-Origin header.
LargestContentfulPaint.loadTimeRead only: The time the element was loaded.
LargestContentfulPaint.sizeRead only: The intrinsic size of the element returned as the area (width * height).
LargestContentfulPaint.idRead only: The id of the element. This property returns an empty string when there is no id.
LargestContentfulPaint.urlRead only: If the element is an image, the request url of the image.

Methods

This interface also inherits methods from PerformanceEntry.

LargestContentfulPaint.toJSON(): Returns the above properties as JSON.

Examples

The following example shows how to create a PerformanceObserver that listens for largest-contentful-paint entries and logs the LCP value to the console.

This example also demonstrates how to include buffered entries (those that ocurred before observer() was called), which is done by setting the buffered option to true.

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 lcp;

  const po = new PerformanceObserver((entryList) => {
    const entries = entryList.getEntries();
    const lastEntry = entries[entries.length - 1];

    // Update `lcp` to the latest value, using `renderTime` if it's available,
    // otherwise using `loadTime`. (Note: `renderTime` may not be available on
    // image elements loaded cross-origin without the `Timing-Allow-Origin` header.)
    lcp = lastEntry.renderTime || lastEntry.loadTime;
  });

  po.observe({type: 'largest-contentful-paint', buffered: true});

  // Send data to the server.
  addEventListener('visibilitychange', function fn() {
    if (lcp && document.visibilityState === 'hidden') {
      console.log('LCP:', lcp);
      removeEventListener('visibilitychange', fn, true);
    }
  }, true);
} catch (e) {
  // Do nothing if the browser doesn't support this API.
}

Specifications

Specification
Largest Contentful Paint # sec-largest-contentful-paint-interface

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
`LargestContentfulPaint`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`element`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`id`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`loadTime`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`renderTime`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`size`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`toJSON`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0
`url`	77	79	No	No	Yes	No	77	77	No	Yes	No	12.0