PerformanceResourceTiming.fetchStart

The fetchStart read-only property represents a timestamp immediately before the browser starts to fetch the resource.

If there are HTTP redirects the property returns the time immediately before the user agent starts to fetch the final resource in the redirection.

Note: This feature is available in Web Workers

Value

A DOMHighResTimeStamp immediately before the browser starts to fetch the resource.

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-fetchstart

Browser compatibility

BCD tables only load in the browser