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 bowser 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 1
The definition of 'requestStart' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support. 43 (Yes) 40 10 32 No support
Feature Android Edge Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support. 4.4 (Yes) 42 ? 10.0 32 No support

Document Tags and Contributors

 Contributors to this page: abbycar, rolfedh, AFBarstow
 Last updated by: chrisdavidmills,