PerformanceResourceTiming: responseEnd property

Value

A DOMHighResTimeStamp immediately after the browser receives the last byte of the resource or immediately before the transport connection is closed, whichever comes first.

Description

The responseEnd property is available for cross-origin requests without the Timing-Allow-Origin HTTP response header, except for navigations of cross-origin <iframe> elements.

Cross-origin iframes

For a cross-origin <iframe>, if the iframe's document is served with a Timing-Allow-Origin header that allows the embedding page's origin, responseEnd is the time immediately after the browser receives the last byte of that document.

Without this header, the precise time isn't reported, because it could reveal how the user interacted with the frame. Instead, the browser reports a fallback entry once the iframe's load event fires. In this entry, startTime is the time the iframe started navigating, and responseEnd is the time the iframe finished loading, including all of its subresources. The other timestamps, as well as the encodedBodySize and decodedBodySize properties, are 0.

Examples

Measuring time to fetch (without redirects)

The responseEnd and fetchStart properties can be used to measure the overall time it took to fetch the final resource (without redirects). If you want to include redirects, the overall time to fetch is provided in the duration property.

const timeToFetch = entry.responseEnd - entry.fetchStart;

Example using a PerformanceObserver, which notifies of new resource performance entries as they are recorded in the browser's performance timeline. Use the buffered option to access entries from before the observer creation.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    const timeToFetch = entry.responseEnd - entry.fetchStart;
    if (timeToFetch > 0) {
      console.log(`${entry.name}: Time to fetch: ${timeToFetch}ms`);
    }
  });
});

observer.observe({ type: "resource", buffered: true });

Example using Performance.getEntriesByType(), which only shows resource performance entries present in the browser's performance timeline at the time you call this method:

const resources = performance.getEntriesByType("resource");
resources.forEach((entry) => {
  const timeToFetch = entry.responseEnd - entry.fetchStart;
  if (timeToFetch > 0) {
    console.log(`${entry.name}: Time to fetch: ${timeToFetch}ms`);
  }
});

Specifications

Browser compatibility

See also

• Timing-Allow-Origin
• Resource timing