PerformanceResourceTiming: connectEnd property
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2017.
Note: This feature is available in Web Workers.
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 TLS 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 noTiming-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;
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 tcp = entry.connectEnd - entry.connectStart;
if (tcp > 0) {
console.log(`${entry.name}: TCP handshake duration: ${tcp}ms`);
}
});
});
observer.observe({ type: "resource", buffered: true });
Example using Performance.getEntriesByType()
, which only shows resource
performance entries present in the browser's performance timeline at the time you call this method:
const resources = performance.getEntriesByType("resource");
resources.forEach((entry) => {
const tcp = entry.connectEnd - entry.connectStart;
if (tcp > 0) {
console.log(`${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