PerformanceElementTiming.renderTime

The renderTime read-only property of the PerformanceElementTiming interface returns the render time of the associated element.

A DOMHighResTimeStamp with the render time of the element.

For images this will be the image rendering timestamp. This is defined as the next paint that occurs after the image becomes fully loaded. If the timing allow check fails (as defined by the Timing-allow-origin header) this will return 0.

For text nodes this will be the text rendering timestamp. This is defined as when the element becomes text painted.

In this example calling entry.renderTime returns the render time of the image element.

<img src="image.jpg" alt="a nice image" elementtiming="big-image" id="myImage">

const observer = new PerformanceObserver((list) => {
  let entries = list.getEntries().forEach(function (entry) {
    if (entry.identifier === "big-image") {
      console.log(entry.renderTime);
    }
  });
});
observer.observe({ entryTypes: ["element"] });