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

Value

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

Examples

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

function printPerformanceEntries() {
  // Use getEntriesByType() to just get the "resource" events
  performance.getEntriesByType("resource")
    .forEach((entry) => {
      printStartAndEndProperties(entry);
    });
}

function printStartAndEndProperties(perfEntry) {
  // Print timestamps of the *start and *end properties
  properties = ["connectStart", "connectEnd",
                "domainLookupStart", "domainLookupEnd",
                "fetchStart",
                "redirectStart", "redirectEnd",
                "requestStart",
                "responseStart", "responseEnd",
                "secureConnectionStart"];

  for (const property of properties) {
    // Log the property
    console.log(`${property} = ${perfEntry[property] ?? "NOT supported"}`);
  }
}

Specifications

Specification
Resource Timing Level 2
# dom-performanceresourcetiming-requeststart

Browser compatibility

BCD tables only load in the browser