PerformanceResourceTiming.connectEnd

The connectEnd read-only property returns the timestamp immediately after the browser finishes establishing the connection to the server to retrieve the resource. The timestamp value includes the time interval to establish the transport connection, as well as other time intervals such as SSL handshake and SOCKS authentication.

Value

The connectEnd property can have the following values:

  • A DOMHighResTimeStamp representing the time after a connection is established.
  • 0 if the resource was instantaneously retrieved from a cache.
  • 0 if the resource is a cross-origin request and no Timing-Allow-Origin HTTP response header is used.

Examples

Measuring TCP handshake time

The connectEnd and connectStart properties can be used to measure how long it takes for the TCP handshake to happen.

const tcp = entry.connectEnd - entry.connectStart;

Using a PerformanceObserver:

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    const tcp = entry.connectEnd - entry.connectStart;
    if (tcp > 0) {
      console.log(`${entry.name}: TCP handshake duration: ${tcp}ms`);
    }
  });
});

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

Or 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 tcp = entry.connectEnd - entry.connectStart;
  if (tcp > 0) {
    console.log(`${entry.name}: TCP handshake duration: ${tcp}ms`);
  }
});

Cross-origin timing information

If the value of the connectEnd property is 0, the resource might be a cross-origin request. To allow seeing cross-origin timing information, the Timing-Allow-Origin HTTP response header needs to be set.

For example, to allow https://developer.mozilla.org to see timing resources, the cross-origin resource should send:

Timing-Allow-Origin: https://developer.mozilla.org

Specifications

Specification
Resource Timing
# dom-performanceresourcetiming-connectend

Browser compatibility

BCD tables only load in the browser

See also