Web/API/PerformanceResourceTiming/requestStart

The requestStart read-only property returns a timestamp of the time immediately before the browser starts requesting the resource from the server, cache, or local resource. If the transport connection fails and the browser retires the request, the value returned will be the start of the retry request.

There is no end property for requestStart.

Note: This feature is available in Web Workers.

Syntax

resource.requestStart;

Return value

A DOMHighResTimeStamp representing the time immediately before the browser starts requesting the resource from the server

Example

In the following example, the value of the *Start and *End properties of all "resource" type events are logged.

function print_PerformanceEntries() {
  // Use getEntriesByType() to just get the "resource" events
  var p = performance.getEntriesByType("resource");
  for (var i=0; i < p.length; i++) {
    print_start_and_end_properties(p[i]);
  }
}
function print_start_and_end_properties(perfEntry) {
  // Print timestamps of the PerformanceEntry *start and *end properties 
  properties = ["connectStart", "connectEnd",
                "domainLookupStart", "domainLookupEnd",
                "fetchStart", 
                "redirectStart", "redirectEnd",
                "requestStart", 
                "responseStart", "responseEnd",
                "secureConnectionStart"];

  for (var i=0; i < properties.length; i++) {
    // check each property
    var supported = properties[i] in perfEntry;
    if (supported) {
      var value = perfEntry[properties[i]];
      console.log("... " + properties[i] + " = " + value);
    } else {
      console.log("... " + properties[i] + " = NOT supported");
    }
  }
}

Specifications

Specification	Status	Comment
Resource Timing Level 1The definition of 'requestStart' in that specification.	Candidate Recommendation	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`requestStart`	Chrome Full support 43	Edge Full support 12	Firefox Full support 40	IE No support No	Opera Full support 30	Safari Full support 11	WebView Android Full support 43	Chrome Android Full support 43	Firefox Android Full support 42	Opera Android Full support 30	Safari iOS Full support 11	Samsung Internet Android Full support 4.0

Legend

Full support: Full support
No support: No support

PerformanceResourceTiming.requestStart by Mozilla Contributors is licensed under CC-BY-SA 2.5.